COMSOL Multiphysics
Release Notes

COMSOL Multiphysics Release Notes© 1998–2018 COMSOL
Protected by patents listed on www.comsol.com/patents, and U.S. Patents 7,519,518; 7,596,474;
7,623,991; 8,219,373; 8,457,932; 8,954,302; 9,098,106; 9,146,652; 9,323,503; 9,372,673; and9,454,625. Patents pending.
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pursuant to the ODB++ Solutions Development Partnership General Terms and Conditions. ODB++ is atrademark of Mentor Graphics Corporation.
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Version: COMSOL 5.4

Contact Information
Visit the Contact COMSOL page at www.comsol.com/contact to submit generalinquiries, contact Technical Support, or search for an address and phone number. You canalso visit the Worldwide Sales Offices page at www.comsol.com/contact/offices foraddress and contact information.
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Part number: CM010001

C o n t e n t s
Chapter 1: Release Notes
New Products

12

COMSOL Compiler™. . . . . . . . . . . . . . . . . . . . . 12
The Composite Materials Module . . . . . . . . . . . . . . . . 12
COMSOL Multiphysics

13

General New Functionality . . . . . . . . . . . . . . . . . . . 13
New Functionality in the Application Builder . . . . . . . . . . . . 13
New Functionality in COMSOL Server™

. . . . . . . . . . . . . 15

New and Improved General Functionality in COMSOL Multiphysics . . . 15
New Functionality in the Physics Interfaces . . . . . . . . . . . . . 17
New Geometry and Mesh Functionality . . . . . . . . . . . . . . 18
New and Updated Operators, Functions, and Definitions . . . . . . . 19
New Functionality in Studies and Solvers . . . . . . . . . . . . . . 19
New and Improved Results and Visualization Functionality . . . . . . . 22®
New Java API Methods . . . . . . . . . . . . . . . . . . . . 24
General Backward Compatibility Considerations . . . . . . . . . . . 24
Backward Compatibility with Version 5.3a . . . . . . . . . . . . . 25
Backward Compatibility with Version 5.3. . . . . . . . . . . . . . 26
Backward Compatibility with Version 5.2a . . . . . . . . . . . . . 27
Backward Compatibility with Version 5.2. . . . . . . . . . . . . . 28
Backward Compatibility with Version 5.1. . . . . . . . . . . . . . 29
Backward Compatibility with Version 5.0. . . . . . . . . . . . . . 30
Backward Compatibility with Version 4.4. . . . . . . . . . . . . . 31
Backward Compatibility with Version 4.3b . . . . . . . . . . . . . 32
Backward Compatibility with Version 4.3a . . . . . . . . . . . . . 33
Backward Compatibility with Version 4.3. . . . . . . . . . . . . . 35
AC/DC Module

36

New Functionality in Version 5.4 . . . . . . . . . . . . . . . . . 36
Backward Compatibility with Version 5.2 and older. . . . . . . . . . 37
Backward Compatibility with Version 5.0 and older. . . . . . . . . . 38

CONTENTS | 3

Acoustics Module

40

New Functionality in Version 5.4 . . . . . . . . . . . . . . . . . 40
New and Updated Model Examples in 5.4 . . . . . . . . . . . . . 41
Backward Compatibility with Version 5.3a . . . . . . . . . . . . . 42
Backward Compatibility with Version 5.3. . . . . . . . . . . . . . 42
Backward Compatibility with Version 5.2. . . . . . . . . . . . . . 42
Backward Compatibility with Version 5.1. . . . . . . . . . . . . . 42
Backward Compatibility with Version 4.3a and Older . . . . . . . . . 43
Backward Compatibility with Version 4.3. . . . . . . . . . . . . . 43
Batteries & Fuel Cells Module

44

New Functionality in Version 5.4 . . . . . . . . . . . . . . . . . 44
New and Updated Applications and Models in Version 5.4 . . . . . . . 46
Backward Compatibility with Version 5.3a . . . . . . . . . . . . . 47
CAD Import Module, Design Module, and LiveLink™ Products
for CAD48

New Functionality in Version 5.4 . . . . . . . . . . . . . . . . . 48
New Functionality in LiveLink™ for AutoCAD® in Version 5.4 . . . . . 48
New Functionality in LiveLink™ for Inventor® in Version 5.4 . . . . . . 48
New Functionality in LiveLink™ for PTC® Creo® Parametric™ in
Version 5.4. . . . . . . . . . . . . . . . . . . . . . . . 49
New Functionality in LiveLink™ for PTC® Pro/ENGINEER® in
Version 5.4. . . . . . . . . . . . . . . . . . . . . . . . 50
New Functionality in LiveLink™ for Revit® in Version 5.4 . . . . . . . 50
LiveLink™ for Solid Edge® . . . . . . . . . . . . . . . . . . . 50
LiveLink™ for SOLIDWORKS® . . . . . . . . . . . . . . . . . 51
Backward Compatibility with Previous Versions . . . . . . . . . . . 51
CFD Module

53

New Functionality in Version 5.4 . . . . . . . . . . . . . . . . . 53
New Model in Version 5.4. . . . . . . . . . . . . . . . . . . . 54
Backward Compatibility with Version 5.3a . . . . . . . . . . . . . 54
Backward Compatibility with Version 5.0. . . . . . . . . . . . . . 55
Backward Compatibility with Version 4.4. . . . . . . . . . . . . . 55
Backward Compatibility with Version 4.3b . . . . . . . . . . . . . 56
Backward Compatibility with Version 4.3a . . . . . . . . . . . . . 57
Backward Compatibility with Version 4.3. . . . . . . . . . . . . . 57

4 | CONTENTS

Chemical Reaction Engineering Module

62

New Functionality in Version 5.4 . . . . . . . . . . . . . . . . . 62
New Application and Updated Models in Version 5.4 . . . . . . . . . 63
Backward Compatibility with Version 5.3a and Earlier . . . . . . . . . 64
Backward Compatibility with Version 5.0 and Earlier . . . . . . . . . 64
Corrosion Module

68

New Functionality in Version 5.4 . . . . . . . . . . . . . . . . . 68
New and Updated Models in Version 5.4. . . . . . . . . . . . . . 69
Backward Compatibility with Earlier Versions . . . . . . . . . . . . 70
ECAD Import Module

71

New Functionality in Version 5.4 . . . . . . . . . . . . . . . . . 71
Backward Compatibility with Version 5.3a . . . . . . . . . . . . . 71
Backward Compatibility with Version 5.2a . . . . . . . . . . . . . 71
Backward Compatibility with Version 5.0. . . . . . . . . . . . . . 71
Electrochemistry Module

72

New Functionality in Version 5.4 . . . . . . . . . . . . . . . . . 72
New and Updated Models in Version 5.4. . . . . . . . . . . . . . 74
Backward Compatibility with Version 5.3a . . . . . . . . . . . . . 74
Electrodeposition Module

75

New Functionality in Version 5.4 . . . . . . . . . . . . . . . . . 75
New and Updated Models in Version 5.4. . . . . . . . . . . . . . 77
Backward Compatibility with Version 5.3a . . . . . . . . . . . . . 77
Fatigue Module

78

New Functionality in Version 5.4 . . . . . . . . . . . . . . . . . 78
Backward Compatibility with Version 5.3. . . . . . . . . . . . . . 78
Geomechanics Module

79

New Functionality in Version 5.4 . . . . . . . . . . . . . . . . . 79
New Models in Version 5.4 . . . . . . . . . . . . . . . . . . . 80
Heat Transfer Module81

New and Improved Functionality in Version 5.4 . . . . . . . . . . . 81
New Applications in Version 5.4 . . . . . . . . . . . . . . . . . 87

CONTENTS | 5

Updated Applications in Version 5.4 . . . . . . . . . . . . . . . 88
Backward Compatibility with Version 5.3a . . . . . . . . . . . . . 89
Backward Compatibility with Version 5.3. . . . . . . . . . . . . . 91
Backward Compatibility with Version 5.2a . . . . . . . . . . . . . 93
Backward Compatibility with Version 5.2. . . . . . . . . . . . . . 93
Backward Compatibility with Version 5.1. . . . . . . . . . . . . . 94
Backward Compatibility with Version 5.0. . . . . . . . . . . . . . 95
Backward Compatibility with Version 4.4. . . . . . . . . . . . . . 97
Backward Compatibility with Version 4.3b . . . . . . . . . . . . . 99
Backward Compatibility with Version 4.3a . . . . . . . . . . . . . 99

6 | CONTENTS

Backward Compatibility with Version 4.3. . . . . . . . . . . . .

100

Obsolete Features . . . . . . . . . . . . . . . . . . . . .

102

MEMS Module

103

New Functionality in Version 5.4 . . . . . . . . . . . . . . . .

103

New Models in Version 5.4 . . . . . . . . . . . . . . . . . .

107

Backward Compatibility with Version 5.2. . . . . . . . . . . . .

108

Backward Compatibility with Version 4.3b . . . . . . . . . . . .

108

Microfluidics Module

109

New Functionality in Version 5.4 . . . . . . . . . . . . . . . .

109

Backward Compatibility with Version 5.3a . . . . . . . . . . . .

109

Backward Compatibility with Version 4.3a . . . . . . . . . . . .

110

Backward Compatibility with Version 4.3. . . . . . . . . . . . .

110

Mixer Module

111

New Functionality in Version 5.4 . . . . . . . . . . . . . . . .

111

Molecular Flow Module

112

Backward Compatibility with Version 5.0 and Earlier . . . . . . . .

112

Multibody Dynamics Module

113

New Functionality in Version 5.4 . . . . . . . . . . . . . . . .

113

Nonlinear Structural Materials Module

115

New Functionality in Version 5.4 . . . . . . . . . . . . . . . .

115

New Models in Version 5.4 . . . . . . . . . . . . . . . . . .

116

Optimization Module

118

New Functionality in Version 5.4 . . . . . . . . . . . . . . . .

118

New and Updated Models in Version 5.4. . . . . . . . . . . . .

119

Backward Compatibility with Version 4.3a . . . . . . . . . . . .

119Particle Tracing Module

120

New Functionality in Version 5.4 . . . . . . . . . . . . . . . .

120

New Applications in Version 5.4 . . . . . . . . . . . . . . . .

120

Backward Compatibility with Version 5.3 and Earlier . . . . . . . .

120

Backward Compatibility with Version 5.2a and Earlier . . . . . . . .

121

Backward Compatibility with Version 5.2. . . . . . . . . . . . .

122

Backward Compatibility with Version 5.1. . . . . . . . . . . . .

122

Backward Compatibility with Version 5.0 and Earlier . . . . . . . .

123

Pipe Flow Module

124

Backward Compatibility with Version 5.1 and older. . . . . . . . .

124

Plasma Module

125

New Functionality in Version 5.4 . . . . . . . . . . . . . . . .

125

New and Updated Applications and Models in Version 5.4 . . . . . .

125

Backward Compatibility with Version 5.3a and Earlier . . . . . . . .

126

Backward Compatibility with Version 5.3 and Earlier . . . . . . . .

126

Backward Compatibility with Version 5.2 and Earlier . . . . . . . .

127

Backward Compatibility with Version 5.1. . . . . . . . . . . . .

127

Backward Compatibility with Version 4.4. . . . . . . . . . . . .

127

Ray Optics Module

129

New Functionality in Version 5.4 . . . . . . . . . . . . . . . .

129

New Applications in Version 5.4 . . . . . . . . . . . . . . . .

131

Backward Compatibility with Version 5.3 and Earlier . . . . . . . .

131

Backward Compatibility with Version 5.2a and Earlier . . . . . . . .

132

Backward Compatibility with Version 5.2. . . . . . . . . . . . .

133

Backward Compatibility with Version 5.0. . . . . . . . . . . . .

135

RF Module

136

New Functionality in Version 5.4 . . . . . . . . . . . . . . . .

136

New and Updated Models in Version 5.4. . . . . . . . . . . . .

138

CONTENTS | 7

8 | CONTENTS

Rotordynamics Module

141

New Functionality in Version 5.4 . . . . . . . . . . . . . . . .

141

New Models in Version 5.4 . . . . . . . . . . . . . . . . . .

142

Semiconductor Module

144

New Functionality in Version 5.4 . . . . . . . . . . . . . . . .

144

New Models in Version 5.4 . . . . . . . . . . . . . . . . . .

147

Structural Mechanics Module

149

New Functionality in Version 5.4 . . . . . . . . . . . . . . . .

149

New Models in Version 5.4 . . . . . . . . . . . . . . . . . .

154

Backward Compatibility with Version 5.2. . . . . . . . . . . . .

155

Backward Compatibility with Version 4.3b . . . . . . . . . . . .

156

Backward Compatibility with Version 4.3a . . . . . . . . . . . .

156

Subsurface Flow Module

157

New Functionality in Version 5.4 . . . . . . . . . . . . . . . .

157

New Models in Version 5.4 . . . . . . . . . . . . . . . . . .

158

Backward Compatibility with Version 5.3a and Earlier . . . . . . . .

158

Wave Optics Module

159

New Functionality in Version 5.4 . . . . . . . . . . . . . . . .

159

New and Updated Models in Version 5.4. . . . . . . . . . . . .

162

Material Library163

New and Updated Material Data in Version 5.4 . . . . . . . . . .

163

LiveLink™ for MATLAB®

164

New Functionality in Version 5.4 . . . . . . . . . . . . . . . .

164

Backward Compatibility with Version 5.2. . . . . . . . . . . . .

165

Backward Compatibility with Version 5.0. . . . . . . . . . . . .

165

The COMSOL API for Use with Java®

166

COMSOL 5.4 API Changes . . . . . . . . . . . . . . . . . .

166

COMSOL 5.3a API Changes

167. . . . . . . . . . . . . . . . .

COMSOL 5.3 API Changes . . . . . . . . . . . . . . . . . .

167

COMSOL 5.2a API Changes. . . . . . . . . . . . . . . . .

167

COMSOL 5.1 API Changes . . . . . . . . . . . . . . . . . .

168

COMSOL 5.0 API Changes . . . . . . . . . . . . . . . . . .

171

COMSOL 4.4 API Changes . . . . . . . . . . . . . . . . . .

173

COMSOL 4.3b API Changes . . . . . . . . . . . . . . . . .

174

COMSOL 4.3a API Changes

174. . . . . . . . . . . . . . . . .

COMSOL 4.3 API Changes . . . . . . . . . . . . . . . . . .

175

COMSOL 4.2a API Changes

176. . . . . . . . . . . . . . . . .

COMSOL 4.1 API Changes . . . . . . . . . . . . . . . . . .

177

COMSOL 4.0a Java API Changes . . . . . . . . . . . . . . . .

178

CONTENTS | 9

10 | C O N T E N T S

1Release Notes
COMSOL Multiphysics® version 5.4 includes the all-new COMSOL Compiler™,
extended and improved versions of the Application Builder, COMSOL Server™,
and COMSOL Multiphysics®, a new Composite Materials Module, as well as
updates and improvements for all COMSOL Multiphysics® add-on products.
These Release Notes provide information regarding new functionality in version
5.4 for all COMSOL®software products.

11

New Products
COMSOL Compiler™
Using the new COMSOL Compiler™, you can compile apps developed using theApplication Builder into standalone, executable apps that can be deployed and run on
any supported platform (Windows®, Linux®, and macOS) without a license file. Suchexecutable apps can be deployed within an organization or distributed to a wide range
of users. A license for COMSOL Compiler™ is needed for compiling and creating
executable apps.

The Composite Materials Module
The Composite Materials Module is a new add-on to the Structural Mechanics Module
for simulations of composite materials. This module provides tools for structural (and,together with other add-on products, multiphysics) modeling in laminate and layeredmaterials.
There are two different formulations for layered shells, one that is based on a classicallaminate theory and one that is based on a more complete 3D theory. The former isimplemented in a material model in the existing Shell interface, whereas the latterforms the basis for the new Layered Shell interface.
The user interface includes tools for specifying isotropic and anisotropic material
properties in layered materials together with dedicated visualization tools used todisplay the layers graphically. By combining the Composite Materials Module with theHeat Transfer Module, you get more sophisticated heat transfer and thermal expansion
functionality. Similarly, you can combine the Composite Materials Module with the
AC/DC Module for layered materials functionality within electrostatics and electric
currents. Applications include structural analysis of composite laminates, possibly
coupled to the Heat Transfer Module and the AC/DC Module for multiphysics
analysis of composite materials.

12 |CHAPTER 1: RELEASE NOTESC O M S O L M ult i ph ysi cs
General New Functionality
IMPORT AND EXPORT OF PREFERENCES

You can now import and export your preference settings to make it easier to migrate
preference settings from earlier versions of a model or from one COMSOLMultiphysics installation to another. The Import and Export buttons are available in the
Preferences dialog.
GRAPHICS SERVER IMPROVEMENTS• File export of images and animations when done from an API client (for example,
MATLAB®) no longer requires a graphics server. This is the case both for the exportof result features and when using the new image().export() method. This relaxed
requirement is especially beneficial when running the server on macOS, which does
not support a graphics server.
• COMSOL Multiphysics can now connect to a graphics server. If connecting both
COMSOL Multiphysics and an API client to the same server, they will handle theplotting individually. COMSOL Multiphysics will continue plotting in its window,
and the API client will plot in windows on the server.

New Functionality in the Application Builder
IMPROVEMENTS TO THE FORM EDITOR• All Form objects can now act as Settings Form nodes in the Model Builder, when theShow in Model Builder check box in the Settings window for Form nodes is selected.
• You can now add local declarations and methods in Form objects. Declarations
added from the main Declarations node are considered global and have their values
synchronized between Form instances. Local declarations are useful when you wantdeclarations set in one Form instance to not affect the values of the declarations inother Form instances. Local methods provide a way to share local methods between
form objects without adding them to the global namespace.
• A Center on screen setting is now available in the Size section of the Main Window
feature. When selected, the app is centered in the middle of the desktop uponlaunch.

COMSOL MULTIPHYSICS|

13• The Size setting for Button and Toggle Button form objects has changed its name to
Style. In addition to the existing Small and Large options, there is a new Flat option.
The Flat style is the same size as Large but with a transparent button background andno border. This look appears on Windows and in the web client. The Flat and Large
styles look the same on macOS and Linux.
• You can now specify the background color for Button objects. When Default isselected, the platform controls the background color.
• The Graphics form object toolbar now includes the new Orthotropic Projection toggle
button.
• The GUI Commands part of the Editor Tools window now includes graphics
commands for the new Orthotropic Projection, Show Selection Colors, and Show
Material and Texture functionality.
• The Results Table form object now supports evaluation groups.
IMPROVEMENTS TO THE METHOD EDITOR AND APPLICATION LANGUAGE• All methods can now act as model methods or method calls in the Model Builder,when the Show in Model Builder check box in the Settings window for Method nodes
is selected.
• You can now add command-line arguments to apps and method calls.
• Method inputs of the double types now have an optional unit definition.
• These methods have been added: model.methodCall().methods(), to get allmodel methods in a model, and model.methodCall(String).inputNames(), to
get the names of input parameters of method reference by given method call. Bothmethods return string arrays. These methods simplify dynamic creation of Method
Call features through the external API.
See also the Application Programming Guide for a complete overview of theapplication language for programming methods in the Application Builder.

14 |CHAPTER 1: RELEASE NOTESNew Functionality in COMSOL Server™
• There is now a live search box on the Application Library page for filtering theapplications shown.
• There is an explicit Remember me check box on the web login form that lets users
decide if their session should be persistent or not.
• The installer now verifies that the Windows service details are valid and that theservice account is able to access the installation directory and the shared working
directory.
• There is now an option to send notifications as emails, in addition to the built-in
notifications panel.
• COMSOL Client can now be launched through Run in COMSOL Client links from a
web browser, even for anonymous and automatically logged in users.
• The Application Library now supports sorting in descending order.

New and Improved General Functionality in COMSOL Multiphysics• For improved navigation in models with many nodes, you can create custom
groupings of nodes by adding Group nodes in the model tree. Group nodes can add
organization to the model tree by grouping features that belong together, such asfeatures that belong to a particular part of the geometry or are related to a particular
aspect of the physics.
• It is now possible to add multiple Parameters nodes for grouping parameters fordifferent purposes. You can also exclude parameters in a Parameters node fromparameter selections (in parametric sweeps, for example). Parameter cases can be
added as Case subnodes to use different parameter values in different cases, which isuseful in connection with the new Parameter switch option for parametric sweeps.
• You can now add selection colors using color themes and color settings forselections under Definitions and for nodes in geometry sequences (in the latter case,when the Resulting objects selection check box has been selected) in 2D and 3D. It
is also possible to control if selection colors as well as material colors and texture
should be shown from the Graphics window toolbar and from the View nodes’
settings.
• The Development toolbar now includes a Compare button. Using the comparefunctionality, you can compare the current model or app with the contents of an
MPH-file on the file system, such as an earlier version of the same model or app.

COMSOL MULTIPHYSICS|

15

The comparison then appears in the Comparison Results window, where you can filter
the differences, inspect the details, and export the comparison to an XML-file.
• It is now possible to create Form objects in the Application Builder and use them as
Settings Form nodes under Global Definitions in the Model Builder or as modal dialog
boxes for performing specific tasks. You can add Settings Form nodes and show themas dialog boxes from the Forms section in the Development toolbar. Also, allapplicable methods can now act as model methods in the Model Builder.
• Improved memory allocation for multicore computers, primarily those using
Windows®. It is activated automatically for a multicore architecture but can also be
activated using the Memory allocator settings on the Multicore and Cluster Computer
page in the Preferences dialog box.
• For global parameters, you can now add multiple Parameters nodes for betterorganization of parameters in your models. A Show in parameter selections check box
can be cleared to exclude parameters from a Parameters node to appear in parameterselections. You can also add Case subnodes for parameter cases and switch between
parameter cases to use different sets of parameter values.
• The Select Study page in the Model Wizard has been reorganized to provide a better
structure and overview for selecting a study type.
• The support for model inputs has been extended so that most physical properties
can now act as model inputs and are represented as predefined variables. There is a
new Common Model Inputs node under Global Definitions, where you can view andchange default scalar values for all model inputs. By default, any material using amodel input will now use the common model input. The Common Model Inputs nodeis added automatically when a model input is requested. You can also add Model
Input nodes under a model component to define model inputs locally in all or partof the component’s geometry.
• The Find tool’s dialog box includes a new Advanced tab that provides more specificsearch methods, including filtering to search specifically for node tags, node labels,node names, node types, descriptions, and settings.
• In the Graphics window toolbar for 3D geometries, a new button is available forswitching between orthotropic and perspective projection.
• Timestamps now appear for messages in the Messages window. They can be turned
off using the Add timestamps to messages check box on the General page in the
Preferences dialog box.
• For closable windows in the COMSOL Desktop®, you can now close then using
Ctrl+F4 (Command+W on macOS).

16 |CHAPTER 1: RELEASE NOTES• You can now select multiple rows in tables (in, for example, the Parameters andVariables nodes).
• In the Selection List window, you can now filter the list of objects or entities bychoosing Only List Selected, Only List Visible, or Only List Applicable from the Filter
List menu.
• Selections for Equation View contributions now appear in the Graphics window
when you have selected a single variable in the list under Variables in an Equation
View node’s Settings window.
IMPROVED HANDLING OF BATCH LICENSES

In version 5.4, the way that batch licenses are checked out has changed. In previous
versions, if you submitted a batch job from the operating system command line, a full
COMSOL Multiphysics license was checked out. One such checkout consists, roughly
speaking, of one COMSOL Desktop user interface license and one batch license forcluster and remote computing. In version 5.4, you can submit a batch job from theoperating system command line with only a batch license being checked out. Thismeans that one concurrent user can submit a batch job and still keep working on thesame or a different model in the COMSOL Desktop environment. If a second batch
job is run simultaneously as the first one by the same user, then a second license ischecked out, unless the second batch job is just a parametric variation of the first one,which still check out only one license key.

New Functionality in the Physics Interfaces• The Discretization section in the Settings windows for the main physics interfaces
nodes is now always visible and includes the fundamental settings for controlling theelement (shape function) order and, in some cases, the element type. To access moreadvanced discretization settings, select Advanced Physics Options from the Showmenu in the Model Builder toolbar. The Discretization option has been removed.
• New Reacting Flow, Diluted Species multiphysics coupling feature.
• Updated formulation for the Flux and the No Flux nodes included in the Transportof Diluted Species interface.
- The flux relative to the convective flux is prescribed instead of the total flux.
- The new formulation implies that the nodes can be used on a moving meshgeometry without compensating for the boundary velocity.

COMSOL MULTIPHYSICS|

17• The inverse time step measure variable dt2Inv, solved for in transport interfaces, hasbeen turned into a state variable and is no longer visible in the user interface.
• Go to Source buttons () are now available for the coupled physics interfaces in
multiphysics coupling features.

New Geometry and Mesh Functionality
GEOMETRY FUNCTIONALITY• It is now possible to highlight the results from building a geometry feature by) in the toolbar at the top of Settings
clicking the Highlight Result button (windows for geometry features.
• There is a new virtual geometry operation, Collapse Face Region, in 3D for
automatic detection and removal of narrow regions of faces. You can select it fromthe Virtual Operations menu when right-clicking a 3D Geometry node. By default,
the tolerance is set automatically, but you can also provide a manual tolerance (interms of a maximum width for a narrow region).
• For the Remove Details operation, you can now control whether it is carried out on
the entire object or on a selection of domains, faces, or edges, using only theselection settings in Entities to Process section in the Settings window for Remove
Details.
• For 1D geometries, you can now specify intervals using interval lengths in addition
to specifying coordinates in the Settings window for Interval nodes.
MESHING FUNCTIONALITY• Faster meshing of boundary layers.
• In the Adapt node, you can now choose to perform mesh adaptation on boundaries
and edges, and it is also possible to modify a mesh by adapting it to a specified
isotropic or anisotropic metric.
• You can now refine meshes on edges, faces, and domains interactively for all meshelement types.
• For physics-controlled meshing, you can now control which physics that willcontribute to the meshing in a multiphysics simulation.
• It is now possible to import planar 2D meshes into a 3D component.
• You can now import second-order elements as linear elements for mesh import in2D and 3D using COMSOL Multiphysics files.

18 |CHAPTER 1: RELEASE NOTES• The Adapt, Convert, and Refine operations are now available for imported meshsequences.
• Improved quad meshing through the use of templates for planar equilateraltriangles, quarter circles, and semicircles.
• You can now also create swept meshes in geometries with isolated geometric
entities.
NEW MESHING TUTORIAL

The new tutorial Swept Meshing of a Bracket Geometry demonstrates how to partition
a 3D geometry to create a swept mesh. This tutorial model explores different strategies
for partitioning the geometry and demonstrates how to combine hexahedral andtetrahedral meshes. Application Library path:
COMSOL_Multiphysics/Meshing_Tutorials/bracket_swept_mesh

New and Updated Operators, Functions, and Definitions• For Interpolation functions, the primitive functions and inverse functions are now
available in the Related Functions section (called Random Sampling in earlier
functions). It is now possible to define the primitive function and random samplingof any interpolation function such that there is also only one actual function andonly one argument for values coming from an input file or from a result table.
• For Boundary System nodes that define boundary coordinate systems, you can now
add Reverse Normal and Domain Normal subnodes to reverse or define the normal
direction for some selected boundaries and domains, respectively.
• Bulk viscosity and parameter of nonlinearity are now available as material properties
for air in the Built-In and Liquids and Gases material libraries.

New Functionality in Studies and Solvers
STUDIES AND STUDY STEP FUNCTIONALITY• Parameters can now be separated into groups using multiple Parameters nodes, andfor each group, it is possible to add parameter cases of values as Case subnodes. For
Parametric Sweep nodes, there is a new Parameter switch sweep type by which you
can sweep over those parameter cases.
• Improved mesh adaptation:- The solutions are now stored in a way that is similar to how solutions are stored
for parametric sweeps. A mesh refinement level parameter is automatically added,

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19

which makes result comparisons easier because all the solutions can be obtained
from one data set.
- All adaptation except Rebuild mesh can now also be used with imported meshes.
- A new General modification refinement method in available in mesh adaptation
studies.
- Improved functionality in the Adapt node in meshing sequences. See Meshing
Functionality above.
• The Stop buttons in the Progress window now appear only for levels where stopping
the solution is applicable.
SOLVER FUNCTIONALITY• It is now possible to reuse the sparsity pattern of previously assembled matrices inorder to improve the performance of the solution process. To do so, and if notselected by default, select the Reuse sparsity pattern check box in the Advanced solver
node’s Assembly Settings section.
• The model reduction functionality has been improved and reorganized. You can add
Global Reduced Model Input nodes under Global Definitions to declare global variables
for use as controlling inputs to Reduced Model nodes. It is now possible to define theexpressions for these variables in one place. These expressions will be used both forthe reduced and unreduced version of the model. You can also import reducedorder model files by choosing Reduced Model Import from the Reduced Models menu
on the Global Definition node’s context menu.
• The default values for the Factor in error estimate for the Direct linear solvers is now
1 (it was 400 in earlier versions). This change applies only to direct linear solvers
when used as the main solver. This change works in the direction of easier error tests(it makes the linear solver error estimate 400 times smaller).
• The FFT solver and study steps now support initial expressions. Such initialexpressions make it possible to couple a field to another field. The mapping occurs
before the FFT.
• A transpose-free QMR iterative solver is now available as a TFQMR solver choice in
the Solver list for the Iterative solver nodes. It can be an alternative to GMRES.
TFQMR uses less memory than GMRES, especially for problems where the
GMRES restart number needs to be increased to reach convergence. Problems inthis category are problems where multigrid or other high-quality preconditioners
cannot be used.

20 |CHAPTER 1: RELEASE NOTES• Anderson acceleration is now available with pseudo time stepping in the Fully
Coupled and Segregated solver steps.
• For the boundary element method, a fast and memory-efficient Hierarchical LU
solver or preconditioner is now available.
• You can now add stop conditions to the Time Explicit solver.
• An option to add a scale factor for the residual scaling has been added to the
Dependent Variables nodes in the solver configurations. It can be useful in cases
where convergence is hampered by the residual error.
• For the eigenvalue solver and study steps, you can now select a Real symmetric solver
consistency check check box, which is available when the Use real symmetriceigenvalue solver list is set to Automatic. It can be used to avoid that the eigenvalue
solver assumes a positive definite mass matrix in cases where that condition is notstrictly fulfilled.
• For time-dependent simulations, the maximum time step can now be an expression.
The expression is evaluated while solving and can, for instance, depend on the timeparameter itself.
• Maximum time step control is now available for the time-dependent modal solver.
• The default behavior for the automatic damped Newton method with automatic
scaling has been improved. The old behavior meant updating the weights used fortermination in every iteration. This strategy is sometimes problematic for thedamping logic and can lead to divergence of the nonlinear iterations. The newalgorithm updates the weights only if they change two orders of magnitude, and theautomatic Newton solver is then restarted from the current solution. A new Updateweights for automatic scales check box is available and selected by default for all the
Newton solvers — Automatic (Newton), Automatic highly nonlinear (Newton), andConstant (Newton) — for the stationary and parametric cases. It makes it possible toturn off the update of weights for automatic scales.
• For the detailed solver log, the time-dependent solver now lists any algebraic
variables at the start of the solution process.
CLUSTER AND BATCH FUNCTIONALITY• You can now choose to store the solutions from a cluster simulation on a single nodeinstead of on all nodes, which can be beneficial for memory management, because

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21

memory usage for the solution can otherwise grow linearly with the number ofnodes in the cluster.
• You can now make use of batch licenses from the command line using the new usebatchlic argument.

New and Improved Results and Visualization Functionality
NEW AND IMPROVED DATA SET AND EVALUATION FUNCTIONALITY• You can now add Evaluation Group nodes to create evaluation groups, which provide
a more structured approach to setting up and maintaining numerical evaluation
nodes in a model. You can add numerical evaluation nodes to an Evaluation Groupnode, and the numerical data from those evaluations appear in a special tablewindow for that evaluation group. The evaluation groups can be updated
automatically after the solver has finished using the new Reevaluate all evaluationgroups after solving check box in the Results node’s Settings window. There is also
support for computing the sum of multiple numerical evaluations, for example.
• New Extrusion 1D and Extrusion 2D data sets for extruding a solution from 1D to
2D or 2D to 3D for use in postprocessing. The data set to extrude can be any data
set with an output dimension equal to the Extrusion data set’s dimension.
• You can now use solution-dependent settings in the parameter ranges in the
Parametric Curve and Parametric Surface data sets.
• A Zoom extents check box is now available in the Settings window for the
Export>Animation feature.
• The Eval feature in the COMSOL Multiphysics API can now retrieve data for Shelldata sets.
• Variables for the plane parameters in Surface data sets are now available.
• It is now possible to use solution-dependent expressions in the Contour and
Isosurface data sets.
• Particle Bin and Ray Bin data sets are now available for evaluations of particles andrays in the Particle Tracing Module and the Ray Optics Module and Acoustics
Module, respectively.
• Response Spectrum 2D and Response Spectrum 3D data sets are now available forresponse spectrum analysis in the Structural Mechanics Module.

22 |CHAPTER 1: RELEASE NOTESNEW AND IMPROVED GRAPHICS AND PLOT FUNCTIONALITY• 3D images can now be exported using the glTF file format (GL transmission
format). The images are saved as binary GLB files.
• A new Surface Slit plot type is now available for 3D surface plots where you see theresult of evaluating one expression on one side and another expression on the otherside.
• Improved annotation plots:- In the Settings window for Annotation plot nodes, you can now choose an anchor
point and specify if the label should be horizontal or vertical.
- The point markers are better looking, and the background color and show frame
settings can be inherited from the parent node.
- In the Settings window for 1D Plot Group nodes, you can choose to plot
annotations using the secondary y-axis.
• It is now possible to plot arrows on streamlines, and a new arrowhead arrow typehas been added.
• For isosurface plots, you can now add isosurface-level labels.
• Improved control of the polar plot axis: You can now specify a zero angle (right, up,
left, or down); angular unit (radians or degrees); rotation direction (clockwise orcounterclockwise); and symmetric angle range.
• A parameter indicator now appears to display the solutions time, parameter value,or phase for the currently selected plot in the upper-left corner of the Graphics
window.
• A Selection subnode is now available for the Mesh plot nodes.
• It is now possible to plot points in Particle Trajectory plots so that the sphere radii
have a constant radius when zooming.
• The plot nodes that were previously called Far Field are now called Radiation Pattern
to better reflect their applicability.
• You can now add a variable name for the azimuthal angle to evaluate it in 2D
axisymmetric radiation pattern plots.
• The Plot First, Plot Previous, Plot Next, and Plot Last buttons are now also available
for 1D plots.
• The rendering of graph plots has been improved.
• In the Graphics window for 3D plots, new Rotate Right 90° and Rotate Left 90°
button are now available, and the Go to ZX View button has been replaced by the Go
to XZ View button.

COMSOL MULTIPHYSICS|

23• It is now possible to control the radius scale for points in plots such as Scatter
Volume plots, where a scale factor relative to the automatic radius is available.
• The Far Field plot is now called Radiation Pattern.
• Using the API and methods, you can create Point Data, Line Data, and Surface
Data plots of raw data in the form of point data, element data, and color data. Theseplots can appear in the COMSOL Desktop but cannot be directly created there. You
can also create 2D and 3D Tube Data, Annotation Data, and Arrow Data plots
using methods.
IMPROVED REPORT GENERATION• You can now create your own custom templates for report generation. For example,
you can define a report template that generates reports containing simulation results
only with large plot images and saves it in a dedicated report templates folder foreasy access in future modeling sessions.
• Report image generation no longer uses the Graphics window of the COMSOLDesktop.
• The Progress window in the COMSOL Desktop now tracks the progress of thereport writing stage.
• There is now complete COMSOL API for Java® support for reports.
• In the Comments field in the Properties window of the nodes in the Model Builder
tree, you can now use syntax to add formatting, Greek letters, exponents, and someother special characters to the node comments. The comments will then include thatformatting in model reports.

New Java® API Methods• The ModelUtil.modelsUsedByOtherClients() method returns the tags of themodels used by other clients.
• The view.geom() and view.getSDim() methods return the geometry and thespace dimension for the view, respectively.

General Backward Compatibility Considerations
COMSOL Multiphysics version 5.3a can open MPH-files saved from COMSOLMultiphysics versions 4.0–5.3.
COMSOL Multiphysics version 5.3a can run Java® files saved from COMSOLMultiphysics versions 4.0–5.3. However, the Java® files may need to be modified in

24 |CHAPTER 1: RELEASE NOTES

accordance with information following in this document and may need to berecompiled with the comsol compile command in version 5.3a.

Backward Compatibility with Version 5.3a
ADAPTATION AND ERROR ESTIMATES

The property rmethod has been renamed meshadaptmethod, with additional possible
values. The old property (rmethod) and its values can still be used.
MASS PROPERTIES AND MASS CONTRIBUTIONSIn the Density section, the Integration frame list in previous versions is now called
Density input frame.
In the API, the corresponding property name has been changed from
integrationFrame to densityFrame.
NO FLUX FORMULATION

The formulation of the No Flux feature has been changed in the Transport of Diluted
Species interface in version 5.4 so that the flux relative to the convective flux is set tozero. The new formulation is used when opening a model from a previous session. In
the previous formulation, the total flux was set to zero.
LEGACY FLAG -DCS.LEFTRIGHTSELECTION HAS BEEN REMOVED

The legacy flag -Dcs.leftrightselection for selections of geometric entities using
left-right click has been removed in version 5.4.
AMD ACML LIBRARIESThe AMD ACML library is no longer supported by AMD. It has been replaced bystandard BLAS and LAPACK as an alternative to Intel MKL. On Linux, the BLIS
library is also available. Intel MKL is still the default BLAS library.
STRICTER SOLUTIONINFO VALIDATIONThe SolutionInfo validation now ensures that SolutionInfo.isValid() returns
true before using other SolutionInfo methods, unless stated otherwise in the
documentation of the methods.

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25

Backward Compatibility with Version 5.3
PDE, BOUNDARY ELEMENTS INTERFACE

The PDE, Boundary Elements interface has been reimplemented and improved.
Backward compatibility is provided for MPH files but not for the Java API.
STABILIZATION IN SOME PHYSICS INTERFACES

Model files created in version 5.3 and earlier retain the old stabilization formulation.
The new formulation is obtained by replacing the physics interface with a new one.
The improved stabilization breaks Model Java-file backward compatibility for timedependent models that contain one of the affected physics interfaces. Please contact
COMSOL Support to learn how to retain backward compatibility for your specific
Model Java-file.
STORE SOLUTION ON DISKThe Store solution on disk option has been removed.
FUNCTIONS IN GEOMETRY FEATURES

The button Rebuild with Updated Functions has been removed from the following
geometry features: Parametric Curve, Parametric Surface, and Sweep. Instead, use theRefresh or Clear Functions button in the function features.
In the API, the method importData() is obsolete for the geometry features
ParametricCurve, ParametricSurface, and Sweep. Instead, use the refresh()method in the function features.
PARTICIPATION FACTOR

Support for participation factors in the eigenvalue solver has been replaced by a new
and improved Participation Factors feature, which is available under Definitions>Variable
Utilities in a model component for computing participation factors in structural
simulations.
INTERPOLATION CURVES

For interpolation curves, in the case when relative tolerance is zero (which is thedefault), the algorithm in 5.3a has changed so that the shape of the curve becomessomewhat different (while still interpolating the given points).

26 |CHAPTER 1: RELEASE NOTESITERATIVE SOLVERSFor the iterative solvers, the error handling mechanism has been improved tocontribute to a general robustness of the computation. The improved mechanism isenabled per default and can give the following effects for nonlinear iterations:• Increased total number of linear iterations• Failure with the error “Divergence of the linear iterations”, if the preconditioner isextremely ill-conditioned.
UNITS IN THE SIZE EXPRESSION NODEThe size expression is now interpreted in the model component’s unit system rather
than in the geometry’s unit system. Also, the spatial coordinates (x, y, z, and so on) are
now always in the component’s unit system. In version 5.3, when evaluating on a grid,
the spatial coordinates were in the geometry’s unit system.
STRESS/STRAIN PLOTS

Principal stress/strain plots now evaluate the stresses and strains in the centers of meshelements instead of in the mesh nodes.

Backward Compatibility with Version 5.2a
FRAME DEFINITIONS

In version 5.3a, all frames are always defined. If you open models from version 5.2a or
earlier, there will be a Permanently Define All Frames button under Frames in the General
section of the Component nodes. When you click the button, all frames are defined, andthe button disappears.
FRAME CONTROLIn previous versions of COMSOL Multiphysics, it was possible to apply multiple
frame-controlling physics on the same selection. For example, it was possible to add
two Solid Mechanics interfaces (with the Include geometric nonlinearity option enabled)on the same selection and solve. In this case, an “override rule” was applied between
the controlling physics, effectively meaning that the last physics in the tree had controlof the frame deformation for the overlapping domains. This situation could cause
unexpected results.
In version 5.3, multiple physics interfaces controlling the same frame are not allowedon the same selection and will cause an error when trying to solve. However, it is still
possible to use multiple frame-controlling physics with overlapping selection, but you

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27

now have to explicitly disable frame control on all but one of the physics. This gives
you better control on what is going on. The functionality to disable frame control forphysics has been incorporated in the Settings window for study steps to allow choosing
different physics to control the frame in different study steps.

Frame-Scoped Variables
Certain variables pertaining to frame deformation are now defined with “frame
prefix”. For example, the relative element volume is now called spatial.relVol.
Previously, these variables were added by the physics interface controlling the frame
deformation so they used a “physics prefix” (for example, ale.relVol). For backward
compatibility of old models, the physics interfaces still define the old variables, but they
are aliases of the new frame variables.
API SYNTAX FOR ERROR HANDLINGThe old syntax for an error
feature("foo").feature("prob1").feature("error1")

is no longer supported. Instead, use the following documented syntax:
feature("foo").problem("error1")
FREE QUAD MESHING

Models saved in version 5.2a with the free quad tessellation method set to Automatic(in a Free Quad feature) or face meshing method set to Quadrilateral (in a Swept
feature), will, when opened in 5.3, have the tessellation method or face meshingmethod set to Legacy version 5.2a or Quadrilateral (legacy version 5.2a), respectively.

Backward Compatibility with Version 5.2
FREE QUAD MESH

The new free quad meshing algorithm is used in new models, but for models createdin earlier versions, the legacy algorithm is used instead. The default for the new method
property is therefore auto in new models, and legacy52 in migrated models.
GEOMINFO CHECK() METHOD

The return value of the check() method in GeomInfo has been removed. Now,
check() throws an error if the geometry is invalid.

28 |CHAPTER 1: RELEASE NOTESTHE CONST PROPERTY IN SOLVERSThe const property available for many solvers has been removed in version 5.2a andreplaced with the cname and clist properties, which are string arrays for the constantnames and corresponding constant values, respectively. For the Dependent Variablesnode, the new property initparametersmethod, which can be set to auto (thedefault) or manual, has been added to control automatic synchronization of values ofparameters to use for initial expressions. The Dependent Variables node now also
includes the cname and clist properties.

Backward Compatibility with Version 5.1
CREATING SELECTIONS

In version 5.2, the selresult property replaced the createselection property.
createselection is still supported for backward compatibility.
SELECTIONS IN PART INSTANCESFor backward compatibility for selections in part instances, there is a Keepnoncontributing selections check box, cleared by default, in the Selection Settings sectionof the Settings window for Part Instance nodes. If you select the Keep noncontributing
selections check box, the Keep column is disabled, and the selection is kept if theContribute to value is None. In the COMSOL API, the default is an active Keepnoncontributing selections setting.
MESH PARTS

For backward compatibility regarding STL/VRML import, and for COMSOL API
compatibility, the old user interface for mesh import (with a specified file name andimport properties) and the corresponding properties are available in the COMSOLAPI but not in the COMSOL Desktop, unless it is the active option. This means thatthe old user interface can only be reached if the filename is set in combination with the
STL import type (the API type stlvrml), which cannot be done from the new userinterface.
DORMAND-PRINCE 5 TIME-STEPPING SOLVER

The Dormand-Prince 5 Runge-Kutta solver in 5.1 does not use field norm scaling inversion 5.1 when estimating errors. This means that the errors of, for instance, an ODE
might become very small when solved together with a field with many DOFs, and thetime steps taken might then be too large. In version 5.2a, the Runge-Kutta solver uses
field norm scaling, which means that old models using the Dormand-Prince 5 might

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29

need tighter tolerances to produce results in earlier versions that are similar to those in
5.2a.

Backward Compatibility with Version 5.0
MESH IMPORTThe method used to automatically partition the boundary of imported meshes in 3D
has been improved. If you have an existing model, you can work with it without being
affected. However, if you click the Import button of the Import feature in the meshing
sequence, the file is read again and the new partitioning method is used. The exception
is if the Import feature had Boundary partitioning set to Manual. In this case, themodified parameter values are preserved under the Feature detection setting, whichuses the same algorithm as in version 5.0.
COMSOL tries to map the old selection on boundaries to the new boundaries, but it
is not always possible to do accurately when new faces have appeared or old faces havedisappeared. You may have to manually review and update boundary, edge, and point
selections after reimporting the mesh.
If you have a Java® or MATLAB® program that imports meshes, the number ofgeometric entities may have changed compared to older versions.
SECURITY SETTINGS

In version 5.2a, the Allow external process and libraries check box on the Security pagein the Preferences dialog box is cleared by default to not allow applications to start
external processes on the computer. The default setting in 5.0 is set to allow suchexternal processes.
DISPLAY OF MAX/MIN MARKERS IN PLOTS

The display of max/min markers in plots is now off by default to make plots fit better
when using a small graphics canvas. In previous versions, the display of max/min
markers in plots was on by default.
MERGED MPH-FILE FORMATThe MPHAPP file and MPH file formats have been merged since version 5.1, and allapplication files use the .mph file suffix. You can still open MPHAPP files created inversion 5.0.

30 |CHAPTER 1: RELEASE NOTESBackward Compatibility with Version 4.4
COMSOL SERVERCOMSOL Server from version 4.4 is now called the COMSOL Multiphysics Server.
MESH IMPORTAn edge in an imported mesh that has a common start and end vertex, or that lacks
start and end vertices, is now split into two edges with distinct start and end vertices.
For meshes where this happens, the numbering of all geometric entities may change
when the mesh is rebuilt.
For MPH files created in earlier versions, selections are automatically updated with the
new entity numbers.
LOCAL COORDINATE VALUES

For model components created in version 5.0 and onward, the variable names xi1,
xi2, and xi3 are reserved for the predefined local coordinate variables. To access theprevious behavior (that local coordinate variables do not exist), you can use the API
method model.modelNode(<tag>).defineLocalCoord(false).
TRANSPORT OF DILUTED SPECIES®

Running Java -files from previous versions may fail due to the new default name for
the Transport of Diluted Species interface. This can be avoided by adding a commandthat specifies the identifier in accordance with the name of the interface. For example,
when creating an interface using the old name (chds):
model.physics().create("chds", "DilutedSpecies", "geom1",
new String[][]{{"c"}});

Add the following line to specify the identifier accordingly:
model.physics("chds").identifier("chds");

The Java® API syntax for creating and accessing vectors and tensors in the Transportof Diluted Species interface has changed as well as the syntax for setting physics
properties. This does not affect MPH files. See the backward compatibility notes for
the Chemical Reaction Engineering Module for additional information that also
applies to the Transport of Diluted Species interface.
DOCUMENTATIONThe COMSOL Multiphysics Programming Reference Manual replaces the
COMSOL API for Use with Java ® Reference Manual.

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31

Backward Compatibility with Version 4.3b
MODEL NODES ARE NOW COMPONENT NODESThe Model nodes (as they were called in previous versions), which contained separate
model components in a model file, are called Component nodes in version 5.2a.
CHANGES TO PARAMETRIC SWEEPS

Old models that use stationary parametric sweeps are loaded with the Reuse solution
for previous step list set to Yes. The Run continuation for list is set to the parameter used,
unless the continuation algorithm would not have been used for this model in previous
versions (for example, if multiple parameters are used or if the parameter list is not
monotonous).
CHANGES TO THE PHYSICS SELECTION IN STUDY SETTINGS

The names of the states of a physics interface in the physics tree, which you can modify
under Physics and Variables Selection in the study steps’ settings windows, havechanged:• Provide Degrees of Freedom is now called Disable in Solvers.
• Disable is now called Disable in Model.
REVISED FORMULATION FOR LAMINAR INFLOW AND LAMINAR OUTFLOW

The formulations of the laminar inflow and laminar outflow conditions have beencorrected. The modified formulation gives a more accurate mass flux. Some models
may now produce a slightly different flow field.
Laminar inflow and laminar outflow are available in the fluid flow physics interfaces in
the following modules:• Batteries & Fuel Cells Module• CFD Module• Corrosion Module• Electrochemistry Module• Electrodeposition Module• Heat Transfer Module• Microfluidics Module• Plasma Module• Subsurface Flow Module

32 |CHAPTER 1: RELEASE NOTESNEW DEFAULT FOR GRAPHICS OPTIMIZATION

Under Graphics and Plot Windows in the Preferences dialog box, the default settings in
the Optimize for list is now Quality instead of Performance.
VELOCITY/ACCELERATION INTEGRATION VARIABLE

For the Solid Mechanics interface (and all related multiphysics interfaces) and theTruss interface, the help variable u0 (velocity integration variable) is used in Prescribed
Velocity and Prescribed Acceleration features for Time Dependent study types. Thisvariable computes the displacement for each point where the condition is prescribed.
It is changed to use the full feature scope in order to avoid collisions in cases where
several such features exist within the same model component. As a result, when
opening and running an old model that uses such features together with a segregatedsolver, an error message appears, stating that not all dependent variables occur in atleast one of the segregated solver steps. The relevant action is to manually add thevelocity integration variable to the segregated step containing the corresponding
displacement field. Alternatively, you can regenerate any affected solver sequence.
MATH LIBRARIES ON AMD PROCESSORSMKL is now the default math library on AMD processors. Switching to the ACML
math library for AMD processors might improve performance in some cases.

Backward Compatibility with Version 4.3a
ERROR ESTIMATION CHANGES IN THE SOLVERSThe Automatic method for Check error estimate for direct linear solvers and for Validate
error estimate has changed. For nonlinear and time-dependent problems, theunderlying nonlinear solver does not accept termination for a linear solution step that
does not fulfill the error estimate (unless the step size is very small). The motivation
for this change is that the old method can lead to premature termination of thenonlinear solution process, which in some cases introduces a large error for thecomputed solution.
This change can cause the solvers to take more nonlinear steps for stationary problems
and more time steps for time-dependent problems, and it may also lead to convergenceproblems. For such cases, use the No method to obtain the old behavior. However,doing so can hide numerical problems and potentially lead to large numerical errors.

COMSOL MULTIPHYSICS|33

TERMINATION CRITERION FOR STATIONARY SOLVERSThe default termination criterion for stationary solvers has changed. In 4.3a, thesettings corresponded to Solution; now, the default is Solution or residual. This change
in default termination criterion might affect models created in earlier versions of
COMSOL Multiphysics if you regenerate the solver sequence in 5.2a.
BACKWARD EULER INITIALIZATION TIME STEP

A new setting in the Advanced section of the settings window for the Time-Dependent
Solver, called Fraction of initial step for Backward Euler, provides an option for enteringa dimensionless quantity that determines the size of the time step for the backward
Euler method (in terms of the initial step). This value can improve the accuracy of theinitialization step but can also affect the start-up of some models. The default value is0.001 (this differs from earlier versions, which used a value of 1). When opening
models created in version 4.3a or earlier, the value for this fraction is set to 1 tomaintain compatibility with those versions.
LOADING EXTERNAL PHYSICS BUILDER JAR FILES

External physics builder JAR archives compiled with earlier versions of COMSOLMultiphysics include a manifest file that contains a reference to the CDO library, which
has been removed. To load such JAR files in version 5.2a, you must first do one of thefollowing:• Delete the META-INF/MANIFEST.MF file in the archive source on the filesystem, and then recompile the JAR archive.
• Manually remove the line with org.eclipse.emf.cdo in the METAINF/MANIFEST.MF file in the JAR archive. You can do this directly in a filearchive manager such as 7-Zip or similar.
HIGHLIGHTING GEOMETRY OBJECTS WHEN DRAWING IN 2D

When you have drawn one geometry object on top of another object, toggling of thehighlighting of these objects occurs when you click several times. It is important thatyou click without moving the cursor in a position where the objects overlap in orderto toggle. For example, if you draw a circle (C1) and then draw another smaller circle(C2) inside of C1, then first clicking on C2 may highlight C1. If you click for a second
time without moving the cursor, it will highlight C2. In previous versions, you would
move the cursor after the first click in order to highlight C2.

34 |CHAPTER 1: RELEASE NOTESBackward Compatibility with Version 4.3
NEW TERMINOLOGY FOR CONSTRAINT TYPESThe following constraint types have new names in version 5.2a:• Bidirectional, symmetric is now Apply reaction terms on: All physics (symmetric).
• Unidirectional is now Apply reaction terms on: Individual dependent variables.
WEAK CONSTRAINTS UPDATE FOR THE LAMINAR FLOW INTERFACE

The weak constraint formulations for the following boundary conditions have been
updated:• Symmetry• The Slip option in the Wall feature
These boundary conditions are now formulated using the same set of Lagrange
multipliers as all of the other boundary conditions in the Laminar Flow interface. The
Lagrange multiplier un_lm has been removed.
Models saved in version 4.3 will include un_lm until the model is re-solved. In somecases, occurrences of un_lm in the solver sequence must be replaced manually. This is
the case if un_lm was the only Lagrange multiplier component in a segregated groupor the only Lagrange multiplier component of a Vanka smoother. Alternatively, you
can generate a new automatic solver sequence. Models saved in versions earlier than
4.3 must either be re-solved in version 5.2a for postprocessing, or opened and re-savedin version 4.3 before being opened in version 5.2a.
AUTOMATICALLY CREATED IDENTITY/CONTACT PAIRSThe pairs created by the Form Assembly feature in the geometry can differ from theirforms in 4.3 for certain 3D and 2D geometries. The pairs should now be the same for
the CAD and COMSOL representations.

COMSOL MULTIPHYSICS|

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AC/DC Module
New Functionality in Version 5.4
ELECTRIC CURRENTS, LAYERED SHELL INTERFACEThe new Electric Currents, Layered Shell interface is used to compute electric fields,
currents, and potential distributions in thin conducting layered shells under conditions
where inductive effects are negligible; that is, when the skin depth is much larger than
the studied device. It supports stationary modeling on faces in 3D.
This interface replaces the old Electric Currents, Shell interface, except for models
from version 5.3a or earlier and for piezoresistive modeling. The old interface has beenrenamed Electric Currents, Single Layer Shell and is available in the Model Wizard and
Add Physics dialog box from Piezoresistivity under Structural Mechanics.
ADDITIONAL NEW FUNCTIONALITY• A new geometry part library for a large variation of coil and core shapes is now
available. Important selections, for example, for feed boundaries, are automaticallygenerated. Some examples of generic shapes are shown below.

• The material model for magnetic saturation has been revised so that there is nolonger a need to input both B-H and H-B curves. Only the B-H curve needs to be
input and the (inverse) H-B curve is computed internally when needed. The

36 |CHAPTER 1: RELEASE NOTES

nonlinear magnetic energy and coenergy densities are now also supplied as output
variables.
NEW APPLICATIONS

A new Layered Shell folder has been added to the AC/DC Module Application
Library. The folder contains three examples that use the Electric Currents, Layered
Shell interface. Two of these models are new and showcase a verification model and aplanar PCB coil. The third model showcases the thermal deformation of a circuit,containing a thin coil. This is an update of a model previously available only within the
Structural Mechanics Module and Heat Transfer Module.
• Solid Multilayer Shell Comparison studies the current conduction in a thinmultilayer structure and compares results from the new shell formulation withresults from a volumetric simulation using the Electric Currents interface where theshell layers are treated and meshed as solid (resolving the thickness).
• Planar PCB Coil simulates a spiral coil on a printed circuit board (PCB) involving
several layers and vias between the layers.
• Heating Circuit models a device consisting of an electrically resistive layer
deposited on a glass plate. The layer causes Joule heating when a voltage is applied
to the circuit. The layer’s properties determine the amount of heat produced.

Backward Compatibility with Version 5.2 and older
COIL FEATURES

Multi-Turn Coil features in old models will be mapped to the new Coil feature using the

Homogenized Multi-Turn Conductor model. Single-Turn Coil features in old models
will import as is with a warning that the feature is obsolete and will be removed infuture versions.
The User Defined Coil Geometry subnode, which is available for 3D Coil nodes with theUser-Defined Coil type, is now a domain feature. You can now select coil input andoutput boundaries using the new Input and Output subnodes. The selection is set up
correctly when opening old models.
REMOVED THE OLD INFINITE ELEMENTS FEATURESThe old Infinite Elements feature, which are obsolete since version 4.2, have now been
discontinued and will be automatically removed when opening old models.

AC/DC MODULE|

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Backward Compatibility with Version 5.0 and older
COIL CURRENT CALCULATION

When models saved in previous versions are opened in version 5.1, the Coil Current
Calculation study steps are migrated to Coil Geometry Analysis. Old solutions stored
in the model can still be postprocessed, and the solver sequence will be regenerated
automatically (with a Stationary solver) the first time the study is solved.
The Coil Geometry Analysis study step (formerly Coil Current Calculation) will now
solve for all of the coils in the active interfaces. To solve only for specific coils (specified
using the CoilName property), set the SpecifyCoil property to 1.
The default solver sequence generated by the Coil Geometry Analysis is different inversion 5.1. Code that accesses specific solver features in the generated solver sequence
may need to be reviewed.
OTHER COIL IMPROVEMENTS

Harmonic Perturbation subnodes under coil features (Single-Turn Coil, Multi-Turn Coil)are now global features, so the call to the create method should use the appropriate
space dimension (-1):
model.physics("mf").feature("stcd1").create("hp1","CoilHarmonicPerturbation", -1);

Global features have no selections, so code that accesses the selection of the Harmonic
Perturbation features may need to be reviewed.
Some of the improvements in the 3D Multi-Turn Coil features may require a review ofexisting code that uses the COMSOL API.
Subnodes required to set up the coil features are now added automatically. Existingcode that uses the coil features may need to be updated.
The parameters eCoil and length have been moved from the Multi-Turn Coil features(boundary and domain) to the new subfeature UserDefinedCoilGeometry.
OTHER IMPROVEMENTS

New functionality introduced in version 5.1 is disabled by default when opening
models created in previous versions:• New boundary conditions for Gauge Fixing features• Accurate coil voltage calculation

38 |CHAPTER 1: RELEASE NOTESThis functionality can be enabled using the appropriate inputs in the Settings window.
Refer to the documentation for the individual features for more details.

AC/DC MODULE|

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Acoustics Module
New Functionality in Version 5.4
The following new functionality is available:• The new Port boundary condition is used to excite and absorb acoustic waves thatenter or leave waveguide structures, like ducts and channels. The condition isavailable in the Pressure Acoustics, Frequency Domain interface.
• A new Nonlinear Acoustics Westervelt feature is available with the Pressure
Acoustics, Time Domain interface. This feature can be used to model highamplitude acoustics in the time domain as experienced in some transducers, acoustic
horns, and ultrasound applications. The new functionality also includes shockcapturing stabilization and specialized solver handling.
• The Atmosphere attenuation and the Ocean attenuation fluid models are used tomodel the attenuation for atmospheric air and for sea water. They are included in
the frequency-domain Pressure Acoustics interfaces and the Ray Acoustics interface.
• The new Exterior Field Calculation feature represents an update of the existing FarField Calculation feature.
• The Exterior Field Calculation feature can now be used in all transient Pressure
Acoustics interfaces when combined with a Time to Frequency FFT study step.
• The Pressure Acoustics, Boundary Element interface now has multiphysics
couplings to Thermoviscous Acoustics and Poroelastic Waves as well as Interior
Velocity and Interior Displacement boundary conditions. In addition, all the
impedance models available for the FEM interface are also available for the BEM
interface.
• The linearized Navier-Stokes and Thermoviscous Acoustics physics interfaces now
have an option to use an adiabatic formulation for the governing equations.
• Gradient-term suppression (GTS) stabilization is now available for the Linearized
Navier-Stokes Equation physics interfaces.
• Several updates to the default plots generated by the physics interface of the
Acoustics Module: New color schemes, eigenfrequency list for eigenfrequency
studies, new and updated Exterior Field default plots. The Far-Field plots have beenrenamed to Radiation Pattern plots.
• A new Modulated Gaussian Pulse option is available for background and incident
fields in the transient Pressure Acoustics interfaces.

40 |CHAPTER 1: RELEASE NOTES• The Air and Water, Liquid materials have been updated with acoustics-specificquantities like the value for the bulk viscosity and the coefficient of nonlinearity.
• The Ray Acoustics interface now includes improved absorption/attenuation
calculation method in domains, improved behavior for Rayleigh roughness, new
input for Exterior and Unmeshed Domains material data, and two new options for
the Compute Intensity feature.

New and Updated Model Examples in 5.4• Duct with Right Angled Bend model studies the acoustic behavior of a duct orwaveguide with a right-angled bend. The model uses Port boundary conditions at
the inlet and outlet. The ports can capture and treat nonplane propagating modes
in waveguides, extending the analysis above the first cutoff frequency. The
transmission loss and the scattering coefficients of the system are determined.
• Small Concert Hall Acoustics analyzes the acoustics of a small concert hall using
the Ray Acoustics physics interface. The model setup includes an omnidirectionalsound source, Wall boundary conditions for specular and diffuse scattering, soundpressure evaluation on a boundary, a Receiver data set, an Impulse Response plot,
and an energy decay curve. The results are compared to a simple reverberation time
estimate.
• Lumped Receiver with Full Vibroacoustic Coupling shows the analysis of theinteraction between a vibration isolation mounting and a miniature hearing aid
transducer (a Knowles TEC30033 balanced armature receiver) using a lumped
representation of the transducer. The lumped model is simplified as an equivalent
electroacoustic circuit. The vibration and acoustic characteristics of the lumped
model are then coupled to a multiphysics model of the vibration isolation system toachieve a full system analysis.
• Loudspeaker Driver — Transient Analysis performs a full transient analysis of aloudspeaker driver, which allows the modeling of nonlinear effects. It extends thelinear frequency domain analysis done in the Loudspeaker Driver tutorial model.
The output includes the total harmonic distortion (THD) and the dynamic BL
curve. The model also describes how to calculate the intermodulation distortion(IMD).
• Nonlinear Acoustics — Modeling of the 1D Westervelt Equation shows how to use
the new Nonlinear Acoustics (Westervelt) model in the Pressure Acoustics, Time
Domain physics interface. The model results are compared to an analytical solution.

ACOUSTICS MODULE|

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• The Absorptive Muffler and Perforated Muffler models have been updated to use
the new Port boundary condition.
• Vibrating Particle Water has been updated to use the new Adiabatic formulation
option in the Thermoviscous Acoustics interface.
• In the Helmholtz Resonator with Flow and Ultrasound Flow Meter with Generic
Time-of-Flight Configuration models, the CFD part of the model has been
updated to use the Fully Developed Turbulent Flow Inlet option. This update
significantly simplifies setting up the model.

Backward Compatibility with Version 5.3a
For the Linearized Navier-Stokes interfaces, the override rules for boundary
conditions have changed. To obtain the old behavior of a model, disable the boundary
conditions that should not contribute to the solution.

Backward Compatibility with Version 5.3
For the Linearized Euler, Transient interface, initial conditions are only used for the
dependent variables. The initial conditions for the time derivatives have therefore been
removed. For a model with fields rho, u, and p, remove the Java® lines setting
drho/dt, du/dt, and dp/dt (these parameters change names when the field names
change).

Backward Compatibility with Version 5.2
The default settings have changed for the Incident Pressure Field in the Pressure
Acoustics interfaces. Add the following line to obtain the old behavior of this featurewhen ipf1 is a subfeature to pwr1:
model.physics("acpr").feature("pwr1").feature("ipf1").
set("c", "acpr.c_c");

Backward Compatibility with Version 5.1• Plane Wave Radiation has been removed from the Linearized Potential Flow,
Frequency Domain and Linearized Potential Flow, Transient interfaces in 1D
axisymmetry.
• A new Lagrange multiplier variable (ta.lm_slip) has been added to the slip
conditions in the Thermoacoustics, Frequency Domain interface. If you run a

42 |CHAPTER 1: RELEASE NOTES

model with a segregated solver, you will need to add this variable to the groupcontaining the velocity degree of freedom. You can also regenerate the default
solver. In the API, you need to add comp1_ta_lm_slip to the declaration of thesegregated step; for example, adding:model.sol("sol1").feature("s1").feature("se1").feature("ss1").
set("segvar", new String[]{"comp1_p", "comp1_u", "comp1_T","comp1_ta_lm_slip"});• The Waveguide end impedance option has been removed from 2D, 1D
axisymmetric, and 1D as it had no physical meaning in these space dimensions.

Backward Compatibility with Version 4.3a and Older• The old Perfectly Matched Layer (PML) node that is located under the physics node
has been discontinued. From the next version on, only the Perfectly Matched Layer
nodes defined under the Definitions node are supported.
• In order for the old Perfectly Matched Layer (PML) node to be backward compatible,
the PML feature must be placed after any domain Monopole Source, domain Dipole
Source, or Background Pressure Field nodes.

Backward Compatibility with Version 4.3• The symbols for volume sources for the acoustics monopole (Qm; was Q) and dipole(qd; was q) volume sources for pressure acoustics have changed.
• The default value for the Typical wave speed property in the Acoustic-PiezoelectricInteraction, Frequency Domain interface has changed to 343 m/s.

ACOUSTICS MODULE|

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Batteries & Fuel Cells Module
New Functionality in Version 5.4• A tortuosity option has been added for effective transport parameter correction fordomain nodes modeling transport in porous media. This option is available in thePrimary Current Distribution and Secondary Current Distribution; Tertiary
Current Distribution, Nernst-Planck; Lithium-Ion Battery; Battery with Binary
Electrode; Single Particle Battery; and Electrophoretic Transport interfaces.
• An Equilibrium Potential Handling (Primary Condition) setting has been added to
the Electrode Surface and Porous Electrode Surface nodes. When there are multiple
Electrode Reaction/Porous Electrode Reaction subnodes present, this setting
controls which equilibrium potential will be used in Current Distribution
Initialization studies.
• A new Ion Exchange Membrane domain feature has been added to the Tertiary
Current Distribution, Nernst-Planck interface.
• An improved Ion Exchange Membrane Boundary feature is now available in the
Tertiary Current Distribution, Nernst-Planck interface that supports transport ofmultiple ions across the membrane.
• PARDISO is now the default for the Direct solver in the Current Distribution andBattery interfaces.
• Accurate boundary fluxes have been added to the Electrophoretic Transportinterface.
• New Equilibrium Reaction and Surface Equilibrium Reaction features are available
in the Transport of Concentrated Species interface.
• A new Fast Irreversible Surface Reaction node has been added to the Tertiary
Current Distribution, Nernst-Planck and Transport of Diluted Species interfaces.
• A new Fast Irreversible Electrode Reaction electrode kinetics expression type has
been added to the Electrode Reaction subnode of the Electrode Surface node in theElectroanalysis and Transport of Diluted Species interfaces. The same feature has
also been added to the Internal Electrode Surface and Thin Electrode Surface
features in the Tertiary Current Distribution, Nernst-Planck interface.
• The Electrostatics interface now supports the Frequency Domain, Perturbation
study step.

44 |CHAPTER 1: RELEASE NOTES• The Electric potential dependent variable now uses quadratic elements in the
Tertiary Current Distribution, Nernst-Planck; Lithium-Ion Battery; Battery with
Binary Electrode; and Lead-Acid Battery interfaces.
• A new Heat of Reaction section has been added to the Electrode Reaction andPorous Electrode Reaction nodes in the electrochemistry interfaces. The newsection supports setting the thermoneutral voltage.
• An improved Periodic Condition feature in the Primary Current Distribution;
Secondary Current Distribution; and Tertiary Current Distribution, Nernst-Planckinterfaces provides an option to set periodicity separately for the electrolyte andelectrode phase, and to set the potential offset.
• A new Lumped Battery interface is available. It provides a simplified (compared to,for instance, the Lithium-Ion Battery or Single Particle Battery interfaces) approachto battery modeling.
• A new Battery Equivalent Circuit entry is available in the Model Wizard.
• The Electrical Circuit interface has been added to the Batteries & Fuel Cells
Module.
• The Battery Open Circuit Voltage node in the Electrical Circuit interface is now
available in the Batteries & Fuel Cells Module.
• dEeqdT data for NMC, LTO, and NCA electrodes has been added to the Batteries& Fuel Cells Material Library.
• Updated Eeq and cEeqref data for NCA electrodes in the Batteries & Fuel Cells
Material Library.
• The Circuit Terminal node and Circuit Terminal boundary condition in theElectrode Surface node have been added to the Batteries & Fuel Cells Module.
• The Circuit Terminal operation node in the Single Particle Battery interface has
been added to the Batteries & Fuel Cells Module.
• There is a new Stress and Strain section in the Particle Intercalation node in the
Lithium-Ion Battery and Battery with Binary Electrode interfaces. The section
settings are used to calculate stress and strain variables.
• The default solver for the battery interfaces now has the Reuse sparsity pattern checkbox enabled in the Advanced solver node’s Assembly Settings section. This setting
typically reduces computation time by around 10% for time-dependent models.
• For both Porous Electrode Reaction and Electrode Reaction nodes in the battery
interfaces (Lithium-Ion Battery, Battery with Binary Electrode, Lead-Acid Battery,BATTERIES & FUEL CELLS MODULE|

45

and Single Particle Battery), the Equilibrium Potential Eeq and dEeqdT parameter
inputs are now taken from Materials by default.
• Improved default plots. Vector plots for models not using Porous Electrodedomains now make use of streamline plots with the new arrow feature.
• Updated formulation for the Flux and No Flux nodes included in the mass transportinterfaces.
- The flux relative to the convective flux is prescribed instead of the total flux.
- The new formulation implies that the nodes can be used on a moving meshgeometry without compensating for the boundary velocity.
- Affected interfaces: Transport of Diluted Species; Transport of Diluted Species in
Porous Media; Transport of Concentrated Species; Tertiary Current
Distribution, Nernst-Planck; Electroanalysis; and Electrophoretic Transport.
• Updated equation display for governing equations and boundary conditions in themass transport interfaces. Equations updated to be formulated in terms of the flux
relative to the convective flux.
• The new setting Account for Stefan velocity is available in the Flux, Mass Fraction,
and Electrode Surface Coupling nodes in the Transport of Concentrated Species
interface.

New and Updated Applications and Models in Version 5.4• Discharge and Self-Discharge of a Lead-Acid Battery model updated to use the
new Equilibrium Potential Handling (Primary Condition) setting.
• Parameter Estimation of a Time-Dependent Lumped Battery Model updated touse the new Lumped Battery interface.
• Vanadium Redox Flow Battery updated to use the new Ion Exchange Membrane
domain node, including automatic Donnan potentials at the internal boundaries.
Also, the model now uses the new Fast Irreversible Electrode Reaction kinetics
expression.
• Ohmic Losses and Temperature Distribution in a Passive PEM Fuel Cell model
updated to use the new Thermoneutral Voltage option in the Heat of Reaction
section.
• New Electrode Utilization in a Large Format Lithium-Ion Battery Pouch Celltutorial added.
• Thermal Modeling of a Cylindrical Lithium-Ion Battery in 2D updated to use
the new Lumped Battery interface.

46 |CHAPTER 1: RELEASE NOTES• New Diffusion-Induced Stress in a Lithium-Ion Battery model added. The model
makes use of the new Stress and Strain section in the Particle Intercalation node.
• New Equivalent Circuit Model for a Ni-MH Battery model added. The model
makes use of the new Battery Equivalent Circuit entry in the Model Wizard.

Backward Compatibility with Version 5.3a
For both Porous Electrode Reaction and Electrode Reaction nodes, in the battery
interfaces (Lithium-Ion Battery, Battery with Binary Electrode, Lead-Acid Battery,and Single Particle Battery), the Equilibrium Potential Eeq and dEeqdT parameter
inputs are now taken from Materials by default. This may have an impact on the Java®
API back compatibility if user-defined settings for these two parameters are used.
NO FLUX FORMULATION

The formulation of the No Flux feature has been changed in the mass transportinterfaces in version 5.4 so that the flux relative to the convective flux is set to zero.
The new formulation is used when opening a new model from a previous version. In
the previous formulation, the total flux was set to zero.
Affected interfaces: Transport of Diluted Species, Transport of Diluted Species in
Porous Media, Transport of Concentrated Species, Tertiary Current Distribution,
Electroanalysis, and Electrophoretic Transport.

BATTERIES & FUEL CELLS MODULE|

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CAD Import Module, Design Module,and LiveLink™ Products for CAD
New Functionality in Version 5.4
The CAD file import functionality included with these products has been extended tosupport new versions for some of the supported file formats (see under Read from File,
CAD on www.comsol.com/products/specifications/cad).
CAD IMPORT MODULE GEOMETRY KERNEL UPGRADE

The CAD Import Module, the Design Module, and the LiveLink™ products for CAD
utilize the Parasolid® geometry kernel from Siemens PLM for solid modeling
operations, geometry repair, and defeaturing. (Without these products, a COMSOLnative geometry modeling kernel is used.) The CAD Import Module released with
COMSOL 5.4 includes an upgraded version of the Parasolid kernel. As a result, a
number of stability issues have been fixed, which makes the import of CAD models andsolid operations more robust.

New Functionality in LiveLink™ for AutoCAD® in Version 5.4• The name and value of dimensional parameters that are controlled by a formula in
the CAD file (read-only parameters) can now be transferred to the COMSOLMultiphysics model during synchronization and become available as parameters inthe simulation setup.
• Material selections, which are generated based on the material assignments in the
CAD file, are now also available as object selections in the appropriate input
selection lists of geometry features following the LiveLink™ feature in a geometry
sequence.
• The LiveLink™ interface now supports AutoCAD® 2019.

New Functionality in LiveLink™ for Inventor® in Version 5.4• The name and value of dimensional parameters that are controlled by a formula in
the CAD file (read-only parameters) can now be transferred to the COMSOLMultiphysics model during synchronization and become available as parameters inthe simulation setup.

48 |CHAPTER 1: RELEASE NOTES• Material selections, which are generated based on the material assignments in the
CAD file, are now also available as object selections in the appropriate input
selection lists of geometry features following the LiveLink™ feature in a geometry
sequence.
• The LiveLink™ interface now supports Inventor® 2019.
• The updated tutorial Electrical Heating in a Busbar Assembly now analyzes alarger busbar assembly designed to conduct a direct current from a current source
to the anode in an electrolysis process. Selections defined in the CAD assembly areused to assign materials and boundary settings in the simulation.
- Application Library path:
LiveLink_for_Inventor/Tutorial_Examples/busbar_llinventor

New Functionality in LiveLink™ for PTC® Creo® Parametric™ in
Version 5.4• Support for PTC® Creo® Parametric™ 2.0 by the LiveLink™ interface will be
removed in the next major release of COMSOL Multiphysics®. File import of
PTC® Creo® Parametric™ 2.0 will continue to be supported.
• The name and value of dimensional parameters that are controlled by a formula in
the CAD file (read-only parameters) can now be transferred to the COMSOLMultiphysics model during synchronization and become available as parameters inthe simulation setup.
• Material selections, which are generated based on the material assignments in the
CAD file, are now also available as object selections in the appropriate input
selection lists of geometry features following the LiveLink™ feature in a geometry
sequence.
• Expanding on the functionality that synchronizes selections based on material
assignments to the CAD design in PTC® Creo® Parametric™, the LiveLink™
interface now adds support for user-defined selections. In the added COMSOL
Selections interface in PTC® Creo® Parametric™, you can define selections that aresynchronized to the COMSOL Multiphysics model. You can choose to synchronize
selections for assembly components, features, bodies, faces, edges, or points, whichbecome selections in the model when the design is synchronized with the
COMSOL Multiphysics model.
• The LiveLink™ interface now supports PTC® Creo® Parametric™ 5.0.

CAD IMPORT MODULE, DESIGN MODULE, AND LIVELINK™ PRODUCTS FOR CAD|

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• The new tutorial Two-Pole Three-Phase Induction Motor illustrates how tocompute the torque of a three-phase squirrel-cage induction motor at various
speeds. Tthe torque is computed by averaging the results from simulations
performed on 2D cross sections at several locations along the induction motor. The
3D geometry and selections, which are used for the physics settings, are transferredfrom PTC® Creo® Parametric™ by the LiveLink™ interface. By defining a cutting
plane in the 3D geometry, the 2D geometry for the simulation is generated in the
COMSOL Multiphysics model by the Cross Section operation, which also retains
the selections defined in 3D.
- Application Library path:
LiveLink_for_PTC_Creo_Parametric/Tutorial_Examples/induction_mo
tor_llcreop

New Functionality in LiveLink™ for PTC® Pro/ENGINEER® in
Version 5.4• The name and value of dimensional parameters that are controlled by a formula in
the CAD file (read-only parameters) can now be transferred to the COMSOLMultiphysics model during synchronization and become available as parameters inthe simulation setup.

New Functionality in LiveLink™ for Revit® in Version 5.4• The name and value of mass parameters that are controlled by a formula in the CAD
file (read-only parameters) can now be transferred to the COMSOL Multiphysics
model during synchronization and become available as parameters in the simulation
setup.
• The LiveLink™ interface now supports Revit® 2019.

LiveLink™ for Solid Edge®
NEW FUNCTIONALITY IN VERSION 5.4• The name and value of dimensional parameters that are controlled by a formula in
the CAD file (read-only parameters) can now be transferred to the COMSOLMultiphysics model during synchronization and become available as parameters inthe simulation setup.

50 |CHAPTER 1: RELEASE NOTES• Material selections, which are generated based on the material assignments in the
CAD file, are now also available as object selections in the appropriate input
selection lists of geometry features following the LiveLink™ feature in a geometry
sequence.
• The LiveLink™ interface now supports Solid Edge® 2019.
BACKWARD COMPATIBILITY WITH VERSION 5.0

The default value for the keepfree property of the LiveLinkSolidEdge function is
now set to on. Previously, the default was set to off.

LiveLink™ for SOLIDWORKS®
NEW FUNCTIONALITY IN VERSION 5.4• User-defined selections now support assembly-level pattern features present in the
SOLIDWORKS® assembly files.
• Material selections, which are generated based on the material assignments in the
CAD file, are now also available as object selections in the appropriate input
selection lists of geometry features following the LiveLink™ feature in a geometry
sequence.
• The name and value of dimensional parameters that are controlled by a formula in
the CAD file (read-only parameters) can now be transferred to the COMSOLMultiphysics model during synchronization and become available as parameters inthe simulation setup.

Backward Compatibility with Previous Versions
BACKWARD COMPATIBILITY WITH VERSION 5.3A

The new fillholes property has been added for the Import function. The following
applies:• The combination of the fillholes property set to on and the knit property set tosolid is equivalent to the knit property set to solid in previous versions.
• The combination of the fillholes property set to off and the knit property set
to surface is equivalent to the knit property set to surface in version 5.3a.
• The combination of the fillholes property set to on and the knit property set tosurface is equivalent to the knit property set to surface in version 5.3 andprevious versions.

CAD IMPORT MODULE, DESIGN MODULE, AND LIVELINK™ PRODUCTS FOR CAD|

51

The new fillholes property has been added for the Knit function. The Knit
function with the fillholes property set to on corresponds to the Knit function inprevious versions.
BACKWARD COMPATIBILITY WITH VERSION 5.2

Geometry Repair Tolerances
The geometry repair tolerance can be automatic, relative, or absolute in version 5.2a.
In previous versions, the repair tolerance was always a relative tolerance.
• If you have not set the relative repair tolerance repairtol, you will get the newdefault repair tolerance type: auto. This will result in a valid geometry in almost allcases. In extreme cases, the result can have a different topology than in 5.2.
• In rare cases, if you have set the repairtol tolerance, version 5.2a can fail whenbuilding the geometry. If so, set repairtoltype to auto (select Automatic from theRepair tolerance list) to get the 5.2 behavior.
BACKWARD COMPATIBILITY WITH VERSION 5.0

The default value for the keepfree property of the LiveLinkSOLIDWORKS function
is now set to on. Previously, the default was set to off.

52 |CHAPTER 1: RELEASE NOTES

CFD Module
New Functionality in Version 5.4• Large Eddy Simulation (LES) is now selectable from the Model Wizard. The three
new interfaces LES RBVM (residual-based variational multiscale), LES RBVMWV(residual-based variational multiscale with viscosity), and LES Smagorinsky are allbased on variational multiscale methods.
• Two new transport interfaces, Phase Transport and Phase Transport in PorousMedia, can be coupled to free flow and porous media flow interfaces, respectively,
to simulate n-phase flow.
• New predefined multiphysics coupling between Phase Transport in Porous Mediaand Darcy’s Law interfaces: Multiphase Flow in Porous Media.
• Three new non-Newtonian models for yield-stress fluids: Bingham-Papanastasiou,
Herschel-Bulkley-Papanastasiou, and Casson-Papanastasiou.
• The Fully developed flow option for Inlet and Outlet features is now available for all
turbulence models.
• All turbulence models are available in the Two-Phase Flow, Level Set and Phase
Field interfaces.
• New features in Two-Phase Flow include Interior Wetted Wall for both Level Set
and Phase Field, and Thin Barrier for Level Set. The Wetted Wall and Interior
Wetted Wall features in Two-Phase Flow, Level Set are now compatible with fluidstructure interaction (FSI).
• Other changes in Two-Phase Flow include conservation corrections and linear
shape functions as the new default discretization.
• New formulations for the Mixture Model and Euler-Euler Model interfaces.
• New boundary conditions in the Mixture Model interfaces: Mixture Continuity andPeriodic Flow Condition.
• An Interior Wall boundary condition is now available in the High Mach Number
Flow interfaces.
• Updated formulation for the Flux and No Flux nodes included in the Transport of
Diluted Species and Transport of Concentrated Species interfaces. The flux relative
to the convective flux is prescribed instead of the total flux.

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• A new setting, Account for Stefan velocity, is available in the Flux and Mass Fraction
nodes in the Transport of Concentrated Species interface.
• The Transient with Initialization study, applicable to some of the Turbulent Flowinterfaces, has been renamed Time Dependent with Initialization.
• The new option, Automatic from physics, for Pseudo time stepping, toggles between
On and Off, depending on whether Turbulence model type is set to RANS or None.
• The default solver for the fluid flow interfaces now has the Reuse sparsity patterncheck box enabled in the Advanced solver node’s Assembly Settings section. Thissetting typically reduces computation time by around 10% for time-dependent
models.

New Model in Version 5.4.
The new Two-Phase Flow over a Low Permeable Lens model, under Multiphase
Tutorials in the Application Library, uses the new predefined multiphysics coupling,
Multiphase Flow in Porous Media, to simulate two-phase flow in a porous medium
containing a low permeable lens.

Backward Compatibility with Version 5.3a
MIXTURE MODEL EQUATION FORMULATIONThe Mixture Model equation formulation has been revised to increase the accuracy
and facilitate the solution of a number of problem setups. As a consequence of therevision, old models can return slightly different results in the new version compared
to previous versions.
EULER-EULER MODEL

The results from models using the Euler-Euler Model interfaces may differ in version
5.4 due to the more general formulation for the viscous stress in the momentum
equation for the dispersed phase. The behavior in the old formulation may be
reproduced by dividing the dispersed phase viscosity, μD, by the variable ee.phidPos.
NO FLUX FORMULATION

The formulation of the No Flux feature has been changed in the Transport of Diluted
Species interface in version 5.4 so that the flux relative to the convective flux is set tozero. The new formulation is used when opening a model from a previous session. In
the previous formulation, the total flux was set to zero.

54 |CHAPTER 1: RELEASE NOTESFULLY DEVELOPED FLOW REPLACES LAMINAR INFLOW AND LAMINAR
OUTFLOWThe Laminar inflow and Laminar outflow options on Inlets and Outlets, respectively,
have been replaced with the Fully developed flow option. Models built in versions prior
to 5.4 will contain warnings about obsolete functionality.

Backward Compatibility with Version 5.0
TRANSPORT OF CONCENTRATED SPECIESSee Chemical Reaction Engineering Module.

Backward Compatibility with Version 4.4
INLET FEATURE

The old inlet features still exist, but have been excluded from the physics context
menu. Old models retain old Inlet features, but adding a new Inlet feature comes with
the new functionality. Old Model Java® files create Inlet features of the old types. The
Normal stress condition can still be prescribed on inlets using an Open Boundary or a
Boundary Stress feature.
NEW NAMES FOR MASS TRANSPORT INTERFACES

Running Model Java® files from previous versions may fail due to the new default
names in the Transport of Diluted Species and Transport of Concentrated Species
interfaces. This can be avoided by adding a command that specifies the identifier inaccordance with the Name of the interface. For example, when creating a Transport ofConcentrated Species interface using the old name (chcs):
model.physics().create("chcs", "ConcentratedSpecies", "geom1",
new String[][]{{"wO2", "wH2O", "wN2"}});

Add the following line to specify the identifier accordingly:
model.physics("chcs").identifier("chcs");
WALL DISTANCE EQUATIONThe old Continuity node is still included in the interface but is excluded from thefeature list. Hence, old models retain their old Continuity node when opened inversion 5.4, and old Model Java®files are fully backward compatible.

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EULER-EULER MODEL

The results from models using the Euler-Euler Model interfaces may differ in version
5.4 due to the more general formulation for the viscous stress in the momentum
equation for the dispersed phase. The behavior in the old formulation may be
reproduced by dividing the dispersed phase viscosity, μD, by the variable ee.phidPos.
FULLY DEVELOPED FLOW REPLACES LAMINAR INFLOW AND LAMINAR
OUTFLOWThe Laminar inflow and Laminar outflow options on Inlets and Outlets respectively havebeen replaced with the Fully developed flow option. Models built in versions prior to
5.4 will contain warnings about obsolete functionality.

Backward Compatibility with Version 4.3b
BUBBLE-INDUCED TURBULENCE IN BUBBLY FLOW

Equation terms accounting for bubble-induced turbulence in the Turbulent Bubbly
Flow interface are now added correctly. As a result, models with Turbulent Bubbly
Flow now show higher levels of turbulence.
MIXTURE MODEL EQUATION FORMULATIONThe Mixture Model equation formulation has been revised to increase the accuracy
and facilitate the solution of a number of problem setups. As a consequence of therevision, old models can return slightly different results in the new version than they
did in previous versions.
EULER-EULER MODEL

The results from models using the Euler-Euler Model interfaces may differ in version
5.4 due to the more general formulation for the viscous stress in the momentum
equation for the dispersed phase. The behavior in the old formulation may be
reproduced by dividing the dispersed phase viscosity, μD, by the variable ee.phidPos.
FULLY DEVELOPED FLOW REPLACES LAMINAR INFLOW AND LAMINAR
OUTFLOWThe Laminar inflow and Laminar outflow options on Inlets and Outlets respectively havebeen replaced with the Fully developed flow option. Models built in versions prior to
5.4 will contain warnings about obsolete functionality.

56 |CHAPTER 1: RELEASE NOTESBackward Compatibility with Version 4.3a
MIXTURE MODEL EQUATION FORMULATIONThe Mixture Model equation formulation has been revised to increase the accuracy
and facilitate the solution of a number of problem setups. As a consequence of therevision, old models can return slightly different results in the new version than they
did in previous versions. As part of the revision, a penalty diffusion on the dispersed
phase has been deactivated, because after the other revisions, it made the equation
system too nonlinear and therefore more difficult to converge. However, you can still
activate the penalty diffusion in the Advanced section of the Mixture Model physics
interface settings.
EULER-EULER MODEL

The results from models using the Euler-Euler Model interfaces may differ in version
5.4 due to the more general formulation for the viscous stress in the momentum
equation for the dispersed phase. The behavior in the old formulation may be
reproduced by dividing the dispersed phase viscosity, μD, by the variable ee.phidPos.
FULLY DEVELOPED FLOW REPLACES LAMINAR INFLOW AND LAMINAR
OUTFLOWThe Laminar inflow and Laminar outflow options on Inlets and Outlets respectively havebeen replaced with the Fully developed flow option. Models built in versions prior to
5.4 will contain warnings about obsolete functionality.

Backward Compatibility with Version 4.3
FLUID-STRUCTURE INTERACTION

The Fluid-Structure Interaction (FSI) multiphysics interface has been updated. The
separate vWall field is no longer required and has been removed. FSI models from 4.3
and earlier versions that include Time Dependent study steps will be affected in thefollowing ways:• Model files for Java® will fail. Any reference to the vWall field must be removed.

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• Models older than 4.3 (that is, 4.2a and older) must clear their time-dependent
solutions when opened in 5.4. An alternative procedure is to:- Open the model in version 4.3.
- Right-click any study with a time-dependent study step and selectUpdate Solution.
- Save the model.
- Open the model in version 5.4.
FSI models with only stationary study steps will not be affected. Note that vWall will
still be available as a variable. Hence, references to fsi.vWall made in, for example,
another physics interface still work.
BRINKMAN EQUATIONS AND FREE AND POROUS MEDIA FLOW

The momentum equations in the Brinkman Equations interface and the Free andPorous Media Flow interface have been corrected. The term −Qbr·u/εp2 in the righthand side previously lacked the factor 1/εp2, where εp is the porosity.
REACTING FLOW INTERFACE NAME CHANGE

The Reacting Flow interfaces have been renamed Reacting Flow in Porous Media. If
you open a model using either the Reacting Flow, Diluted Species or the Reacting
Flow, Concentrated Species interface, the interface is renamed Reacting Flow in
Porous Media.
WEAK CONSTRAINTS UPDATE FOR FLUID FLOW INTERFACES

The weak constraint formulations for the following boundary conditions in thefollowing interfaces have been updated:

Laminar Flow and Creeping Flow
• Symmetry• The Slip boundary condition in the Wall feature

Turbulent Flow, k- ε and Turbulent Flow, k- ω
• Symmetry• The Wall functions boundary condition in the Wall feature• The Moving Wall (wall functions) boundary condition in the Wall feature• The Slip boundary condition in the Wall feature

58 |CHAPTER 1: RELEASE NOTESTurbulent Flow, low-Re k- ε and Turbulent Flow, Spalart-Allmaras• Symmetry• The Slip option in the Wall feature

Rotating Machinery• Symmetry• The Slip boundary condition in the Wall feature• The Wall Functions boundary condition in the Wall feature (turbulent flow only)• The Moving Wall (wall functions) boundary condition in the Wall feature (turbulent
flow only)• Rotating Wall (turbulent flow only)

Bubbly Flow
• Symmetry• The Slip boundary condition for the liquid phase in the Wall feature• The Wall Functions boundary condition for the liquid phase in the Wall feature(turbulent flow only)

Mixture Model• Symmetry• The Slip boundary condition for the mixture in the Wall feature• The Wall Functions boundary condition for the mixture in the Wall feature(turbulent flow only)

Euler-Euler Model, Laminar Flow
• Symmetry• The Slip boundary condition for either phase in the Wall feature• The Slip boundary condition for either phase in the Inlet feature

Brinkman Equations and Free and Porous Media Flow
• Symmetry• The Slip boundary condition in the Wall feature

Two-Phase Flow, Level Set• Symmetry• The Slip boundary condition in the Wall feature• The Wetted Wall boundary condition in the Wall feature• The Moving Wetted Wall boundary condition in the Wall feature

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• The Wall Functions boundary condition in the Wall feature (turbulent flow only)• The Moving Wall (wall functions) boundary condition in the Wall feature (turbulent
flow only)

Two-Phase Flow, Phase Field• Symmetry• The Slip boundary condition in the Wall feature• The Wall function boundary condition in the Wall feature (turbulent flow only)• The Moving Wall (wall functions) boundary condition in the Wall feature (turbulent
flow only)

Nonisothermal Flow and Conjugate Heat Transfer• Symmetry• The Slip boundary condition in the Wall feature• The Wall Functions boundary condition in the Wall feature (turbulent flow k-ε andturbulent flow k-ω only)• The Moving Wall (wall functions) boundary condition in the Wall feature (turbulent
flow k-ε and turbulent flow k-ω only)

High Mach Number Flow
• Symmetry• The Slip boundary condition in the Wall feature• The Wall Functions boundary condition in the Wall feature (turbulent flow k-ε only)• The Moving Wall (wall functions) boundary condition in the Wall feature (turbulent
flow k-ε only)
These boundary conditions are now formulated using the same set of Lagrange
multipliers as all of the other boundary conditions for the dependent velocity variables.
The previously used Lagrange multiplier un_lm has been removed.
When you open models saved in version 4.3, they include un_lm until the model is resolved. In some cases, occurrences of un_lm in the solver sequence must be replaced
manually. This is the case if un_lm was the only Lagrange multiplier component in asegregated group or the only Lagrange multiplier component of a Vanka smoother.
Alternatively, you can generate a new automatic solver sequence. Models saved inversions prior to version 4.3 must either be re-solved in version 5.4 for postprocessing,or opened and re-saved in version 4.3 before being opened in version 5.4.
Weak constraints for the Interior Wall feature are no longer available.

60 |CHAPTER 1: RELEASE NOTESREVISION OF THE TURBULENCE MODELS

The formulations of some variables in the turbulence models have been revised inorder to improve accuracy. Models using a turbulence model can display a different
convergence behavior in version 5.4 than in version 4.3 and the results can differ
slightly between the versions.
EULER-EULER MODEL

The results from models using the Euler-Euler Model interfaces may differ in between
versions 4.3 and 5.4 due to the more general formulation for the viscous stress in the
momentum equation for the dispersed phase. The behavior in the old formulation may
be reproduced by dividing the dispersed phase viscosity, μD, by the variable
ee.phidPos.
FULLY DEVELOPED FLOW REPLACES LAMINAR INFLOW AND LAMINAR
OUTFLOWThe Laminar inflow and Laminar outflow options on Inlets and Outlets respectively havebeen replaced with the Fully developed flow option. Models built in versions prior to
5.4 will contain warnings about obsolete functionality.

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Chemical Reaction Engineering
ModuleNew Functionality in Version 5.4• New features in the Transport of Diluted Species interface: Partition Condition,
Surface Reactions, and Fast Irreversible Surface Reaction.
• New features in the Transport of Concentrated Species interface; Equilibrium
Reaction and Surface Equilibrium Reaction.
• A new Reacting Flow, Diluted Species coupling feature.
• A new User Defined Species feature is available in the Thermodynamics interface.
• The Thermodynamic System feature replaces the Property Package feature. The
feature used for thermodynamics calculation is now called Thermodynamic System.
- The system phases are reflected in the default label. For example, a VaporLiquid System node is created for a system including a vapor and a liquid phase.
• The Thermodynamics node is added automatically when creating athermodynamics feature (Thermodynamic System or User-Defined Species).
• Parameters and functions are sorted under the respective Thermodynamic System
feature.
- Species properties are collected under a node with the species name.
- Mixture properties and Equilibrium Calculation nodes are collected under a
Mixture node.
- Properties for a specific phase are collected in nodes with the name of the phase.
• Improved user interface for controlling the thermodynamic models and property
models in a Thermodynamic System.
- Two settings, Liquid phase model and Gas phase model, are now used to control
the thermodynamic models for two-phase and three-phase systems.
- All property models can be inspected and edited in a table.
• Improved user interface for binary interaction parameters in a Thermodynamic
System.
- All binary interaction parameters currently in use can be inspected and edited ina table.

62 |CHAPTER 1: RELEASE NOTES• Improved user interface for the Maxwell-Stefan diffusivities in the Transport ofConcentrated Species interface. Using the table input, each species pair is clearlyshown.
• Support for creating the new Equilibrium Reaction and Surface Equilibrium
Reaction features (in the Transport of Concentrated Species interface), from theGenerate Space-Dependent Model feature in the Reaction Engineering interface.
• Support for automatic definition of the equilibrium constant is now available in theReaction Engineering interface and the Chemistry interface.
• Support for automatic evaluation of the heat of reactions for isothermal condition
is now available in the Reaction Engineering interface and the Chemistry interface
when fully coupled to a Thermodynamic System.
• Improved sorting of postprocessing variables in mass transport interfaces.
• Updated formulation for the Flux and No Flux nodes included in the mass transportinterfaces.
- The flux relative to the convective flux is prescribed instead of the total flux.
- The new formulation implies that the nodes can be used on a moving meshgeometry without compensating for the boundary velocity.
- Affected interfaces: Transport of Diluted Species, Transport of Diluted Species in
Porous Media, Transport of Concentrated Species, Nernst-Planck Equations,and Electrophoretic Transport.
• Updated equation display for governing equations and boundary conditions in themass transport interfaces. Equations updated to be formulated in terms of the flux
relative to the convective flux.
• A new setting, Account for Stefan velocity, is available in the Flux and Mass Fraction
nodes in the Transport of Concentrated Species interface.

New Application and Updated Models in Version 5.4
New application: Equilibrium Reaction – Gas Phase Conversion of Ethylene toEthanol. This application can be used to investigate how equilibrium compositions areaffected by initial conditions and operating conditions.
The Separation Through Dialysis model has been updated to use the new Partition
Condition feature. The model now includes a single Transport of Diluted Species
interface.

CHEMICAL REACTION ENGINEERING MODULE|

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The Dissociation in a Tubular Reactor model has been updated to use theThermodynamics functionality. The model uses the new User Defined Species feature,
as well as the new automatic definition of the equilibrium constant. The model is now
available in the Thermodynamics folder of the Application Library included with theChemical Reaction Engineering Module.
The HI Batch Reactor model has been updated to use the Thermodynamics
functionality. The model is now available in the Thermodynamics folder of the
Application Library included with the Chemical Reaction Engineering Module.

Backward Compatibility with Version 5.3a and Earlier
NO FLUX FORMULATION

The formulation of the No Flux feature has been changed in the Transport of Diluted
Species interface in version 5.4 so that the flux relative to the convective flux is set tozero. The new formulation is used when opening a model from a previous session. In
the previous formulation, the total flux was set to zero.
Affected interfaces: Transport of Diluted Species, Transport of Diluted Species in
Porous Media, Transport of Concentrated Species, Nernst-Planck Equations, andElectrophoretic Transport.

Backward Compatibility with Version 5.0 and Earlier
REACTION ENGINEERING AND CHEMISTRY INTERFACES

The API syntax for creating surface species has changed. Running Java® files fromprevious versions may fail due to the new default name indexes, including ads forsurface species and s for solids in the Reaction Engineering and Chemistry interfaces.
The surface species names and solid species names need to be changed accordingly in
any Java® code:• Change any species index (s) to (ads)• Change any species index (S) to (s)The following shows an example of the needed code change:
Version 5.0 and earlier:model.physics("re").feature("rch1").set("formula", "A+B(S)=>C+D(s)");model.physics("re").feature("spec1").set("specName", "As(s)");model.physics("chem").feature("rch1").set("formula", "A+B(S)=>C+D(s)");64 |CHAPTER 1: RELEASE NOTES

model.physics("chem").feature("spec1").set("specName", "As(s)");Change this to
Version 5.2 and later:model.physics("re").feature("rch1").set("formula", "A+B(s)=>C+D(ads)");model.physics("re").feature("spec1").set("specName", "As(ads)");model.physics("chem").feature("rch1").set("formula", "A+B(s)=>C+D(ads)");model.physics("chem").feature("spec1").set("specName", "As(ads)");TRANSPORT OF CONCENTRATED SPECIES INTERFACE

Updated Internal Variable Names
The internal variable names of vector and tensor components have changed in theTransport of Concentrated Species interface. In most cases, users will not be affectedby this change. When opening a model file created in a previous version, the previous
variable definitions remain. However, when updating or recomputing the solution,
new variable names will be generated. This means that if any of these variable names
have been used in a user-defined expression or plot, they need to be updated manually
as described below.
In version 5.1, the spatial direction indicator string (x, xy, and so on) has been moved
to the end of the variable name. This applies to all vector and tensor variables generated
by the interface.
For example, the diffusive flux vector components have changed (in 5.0 and earlier)from
tcs.dfluxx_w1, tcs.dfluxy_w1, tcs.dfluxz_w1

to (in 5.2 and later)
tcs.dflux_w1x, tcs.dflux_w1y, tcs.dflux_w1z

and the components of the diffusion tensor, defined by the Fick’s Law diffusion model,
have been changed (in 5.0 and earlier) from
tcs.Dfxx_w1, tcs.Dfxy_w1, tcs.Dfxz_w1, tcs.Dfyx_w1, ...

to (in 5.2 and later)
tcs.Df_w1xx, tcs.Df_w1xy, tcs.Df_w1xz, tcs.Df_w1yx, ...

Java ® API Syntax Changes
The API syntax for setting physics properties has been changed in the Transport ofConcentrated Species interface. Now the property name corresponds to the name of

CHEMICAL REACTION ENGINEERING MODULE|

65

the GUI section containing the property. In order to run Java® files from previous
versions, apply the syntax changes as given in the examples below:
Version 5.0 and earlier:model.physics("tcs").prop("DiffusionModel").setIndex("DiffusionModel","MaxwellStefan", 0);model.physics("tcs").prop("DiffusionModel").setIndex("DiffusionModel","MixtureAveraged", 0);model.physics("tcs").prop("DiffusionModel").setIndex("DiffusionModel","FicksLaw", 0);model.physics("tcs").prop("Convection").setIndex("Convection", "0", 0);model.physics("tcs").prop("Migration").setIndex("Migration", "0", 0);model.physics("tcs").prop("Regularization").setIndex("Regularization", "1",0);

For version 5.2 and later, change this to:model.physics("tcs").prop("TransportMechanism").set("DiffusionModel","MaxwellStefan");model.physics("tcs").prop("TransportMechanism").set("DiffusionModel","MixtureAveraged");model.physics("tcs").prop("TransportMechanism").set("DiffusionModel","FicksLaw");
model.physics("tcs").prop("TransportMechanism").set("Convection", false);
model.physics("tcs").prop("TransportMechanism").set("Migration", false);
model.physics("tcs").prop("AdvancedSettings").set("Regularization", "0");SURFACE REACTIONS INTERFACE

Updated Internal Variable Names
The same pattern for vector and tensor variable name changes, as described in theTransport of Concentrated Species Interface section above, holds true for theSurface Reactions interface in version 5.4.

Java ® API Syntax Changes
The API syntax for setting the diffusion tensor of surface species, the molar mass anddensity of the bulk species, and initial values have been changed in the Surface
Reactions interface.

Setting Diffusion Tensor
The surface species name needs to be included in the first argument of the set method.
In order to run Model Java® files from previous versions, apply the syntax changes asshown in the example below:
Version 5.0 and earlier:model.physics("sr").feature("sp1").set("D_0", new String[]{"Dcs1", "0", "0","0", "Dcs1", "0", "0", "0", "Dcs1"});

66 |CHAPTER 1: RELEASE NOTES

model.physics("sr").feature("sp1").set("D_1", new String[]{"Dcs2", "0", "0","0", "Dcs2", "0", "0", "0", "Dcs2"});For version 5.2 and later, change this to:model.physics("sr").feature("sp1").set("D_cs1", new String[]{"Dcs1", "0","0", "0", "Dcs1", "0", "0", "0", "Dcs1"});model.physics("sr").feature("sp1").set("D_cs2", new String[]{"Dcs2", "0","0", "0", "Dcs2", "0", "0", "0", "Dcs2"});

Setting Molar Mass and Density

The bulk species name needs to be included in the first argument of the setIndex
method. Apply the Java® API syntax changes as shown in the example below:
Version 5.0 and earlier:model.physics("sr").feature("sp1").set("M_0", "Mcb1");
model.physics("sr").feature("sp1").set("M_1", "Mcb2");
model.physics("sr").feature("sp1").set("rho_0", "rhocb1");
model.physics("sr").feature("sp1").set("rho_1", "rhocb2");

For version 5.2 and later, change this to:model.physics("sr").feature("sp1").setIndex("M_cb1", "Mcb1", 0);model.physics("sr").feature("sp1").setIndex("M_cb2", "Mcb2", 0);model.physics("sr").feature("sp1").setIndex("rho_cb1", "rhocb1", 0);model.physics("sr").feature("sp1").setIndex("rho_cb2", "rhocb2", 0);

Setting Initial Values

Apply the Java® API syntax changes as shown in the example below:
Version 5.0 and earlier:model.physics("sr").feature("init1").set("cs1", "cs10");model.physics("sr").feature("init1").set("cs2", "cs20");model.physics("sr").feature("init1").set("cb1", "cb10");model.physics("sr").feature("init1").set("cb2", "cb20");

For version 5.2 and later, change this to:model.physics("sr").feature("init1").setIndex("initcs", "cs10", 0);model.physics("sr").feature("init1").setIndex("initcs", "cs20", 1);
model.physics("sr").feature("init1").setIndex("initcb", "cb10", 0);model.physics("sr").feature("init1").setIndex("initcb", "cb20", 1);

CHEMICAL REACTION ENGINEERING MODULE|

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Corrosion Module
New Functionality in Version 5.4• A tortuosity option has been added for effective transport parameter correction fordomain nodes modeling transport in porous media. This option is available in thePrimary Current Distribution and Secondary Current Distribution; Tertiary
Current Distribution, Nernst-Planck; Lithium-Ion Battery; Battery with Binary
Electrode; Single Particle Battery; and Electrophoretic Transport interfaces.
• An Equilibrium Potential Handling (Primary Condition) setting has been added to
the Electrode Surface and Porous Electrode Surface nodes. When there are multiple
Electrode Reaction/Porous Electrode Reaction subnodes present, this setting
controls which equilibrium potential will be used in Current Distribution
Initialization studies.
• A new Ion Exchange Membrane domain feature has been added to the Tertiary
Current Distribution, Nernst-Planck interface.
• An improved Ion Exchange Membrane Boundary feature is now available in the
Tertiary Current Distribution, Nernst-Planck interface that supports transport ofmultiple ions across the membrane.
• PARDISO is now the default for the Direct solver in the Current Distribution andBattery interfaces.
• Accurate boundary fluxes have been added to the Electrophoretic Transportinterface.
• A new Fast Irreversible Surface Reaction node has been added to the Tertiary
Current Distribution, Nernst-Planck and Transport of Diluted Species interfaces.
• A new Fast Irreversible Electrode Reaction electrode kinetics expression type has
been added to the Electrode Reaction subnode of the Electrode Surface node in theElectroanalysis and Transport of Diluted Species interfaces. The same feature has
also been added to the Internal Electrode Surface and Thin Electrode Surface
features in the Tertiary Current Distribution, Nernst-Planck interface.
• The Electrostatics interface now supports the Frequency Domain, Perturbation
study step.
• The Electric Potential dependent variable now uses quadratic elements in the
Tertiary Current Distribution, Nernst-Planck interface.

68 |CHAPTER 1: RELEASE NOTES• A new Heat of Reaction section has been added to the Electrode Reaction andPorous Electrode Reaction nodes in the electrochemistry interfaces. The newsection supports setting the thermoneutral voltage.
• An improved Periodic Condition feature in the Primary Current Distribution;
Secondary Current Distribution; and Tertiary Current Distribution, Nernst-Planckinterfaces provides an option to set periodicity separately for the electrolyte andelectrode phase, and to set the potential offset.
• Improved point/edge (2D/3D) conditions at the intersection between a dissolving(corroding) Deforming Electrode Surface multiphysics node and a Nondeforming
Boundary multiphysics node.
• The Level Set interface is now available in the Corrosion Module.
• Improved default plots. Vector plots for models not using Porous Electrodedomains now make use of streamline plots with the new arrow feature.
• Updated formulation for the Flux and No Flux nodes included in the mass transportinterfaces.
- The flux relative to the convective flux is prescribed instead of the total flux.
- The new formulation implies that the nodes can be used on a moving meshgeometry without compensating for the boundary velocity.
- Affected interfaces: Transport of Diluted Species: Transport of Diluted Species in
Porous Media, Tertiary Current Distribution, Nernst-Planck; Electroanalysis;
and Electrophoretic Transport.
• Updated equation display for governing equations and boundary conditions in themass transport interfaces. Updated equations are formulated in terms of the flux
relative to the convective flux.

New and Updated Models in Version 5.4
A new Under-Deposit Corrosion model, using the Level Set interface, is now available
with the Corrosion Module Application Library.
A new Localized Corrosion model, using the Level Set interface, is now available with
the Corrosion Module Application Library.

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69

Backward Compatibility with Earlier Versions
NO FLUX FORMULATION

The formulation of the No Flux feature has been changed in the Transport of Diluted
Species interface in version 5.4 so that the flux relative to the convective flux is set tozero. The new formulation is used when opening a model from a previous session. In
the previous formulation, the total flux was set to zero.
Affected interfaces: Transport of Diluted Species; Transport of Diluted Species in
Porous Media; Tertiary Current Distribution, Nernst-Planck; Electroanalysis; andElectrophoretic Transport.

70 |CHAPTER 1: RELEASE NOTESECAD Import Module
New Functionality in Version 5.4• Support for the ODB++(X) and NETEX-G formats will be removed in the next
major release of COMSOL Multiphysics.
• For PCB files (ODB++® and IPC-2581) the import generates domain andboundary selections based on the electrical nets defined in the file.
• The buttons Select All Metal And Dielectric Layers for Import and Clear All Imports havebeen added to the Layers to import table to enable a more efficient workflow whenimporting ECAD files.

Backward Compatibility with Version 5.3a
The elevation property of the Import function is now also initialized when setting
the manualelevation property to off. Previously, it was only initialized when setting
the filename property, the manualelevation property is off, and the value of either
the height or importtype properties is changed.

Backward Compatibility with Version 5.2a
• The default value for the sellayer property of the Import function is now on.
Previously, the default was off.
• The default value for the sellayershow property of the Import function is now
all. Previously, the default was dom.

Backward Compatibility with Version 5.0• The default value for the grouping property of the Import function is now layer.
Previously, the default was all.
• For ODB++® and ODB++(X) files (the type property is odb), new rules apply forthe initialization of the importlayer property of the Import function. Now, only
layers of the types Metal and Dielectric are initialized with the string on in theimportlayer string array. Previously, this also included layers of the type Drill.

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Electrochemistry Module
New Functionality in Version 5.4• A tortuosity option has been added for effective transport parameter correction fordomain nodes modeling transport in porous media. This option is available in thePrimary Current Distribution and Secondary Current Distribution; Tertiary
Current Distribution, Nernst-Planck; Lithium-Ion Battery; Battery with Binary
Electrode; Single Particle Battery; and Electrophoretic Transport interfaces.
• An Equilibrium Potential Handling (Primary Condition) setting has been added to
the Electrode Surface and Porous Electrode Surface nodes. When there are multiple
Electrode Reaction/Porous Electrode Reaction subnodes present, this setting
controls which equilibrium potential will be used in Current Distribution
Initialization studies.
• A new Ion Exchange Membrane domain feature has been added to the Tertiary
Current Distribution, Nernst-Planck interface.
• An improved Ion Exchange Membrane Boundary feature is now available in the
Tertiary Current Distribution, Nernst-Planck interface that supports transport ofmultiple ions across the membrane.
• PARDISO is now the default for the Direct solver in the Current Distribution andBattery interfaces.
• Accurate boundary fluxes have been added to the Electrophoretic Transportinterface.
• A new Fast Irreversible Surface Reaction node has been added to the Tertiary
Current Distribution, Nernst-Planck and Transport of Diluted Species interfaces.
• A new Fast Irreversible Electrode Reaction electrode kinetics expression type has
been added to the Electrode Reaction subnode of the Electrode Surface node in theElectroanalysis and Transport of Diluted Species interfaces. The same feature has
also been added to the Internal Electrode Surface and Thin Electrode Surface
features in the Tertiary Current Distribution, Nernst-Planck interface.
• The Electrostatics interface now supports the Frequency Domain, Perturbation
study step.
• The Electric Potential dependent variable now uses quadratic elements in the
Tertiary Current Distribution, Nernst-Planck interface.

72 |CHAPTER 1: RELEASE NOTES• A new Heat of Reaction section has been added to the Electrode Reaction andPorous Electrode Reaction nodes in the electrochemistry interfaces. The newsection supports setting the thermoneutral voltage.
• An improved Periodic Condition feature in the Primary Current Distribution;
Secondary Current Distribution; and Tertiary Current Distribution, Nernst-Planckinterfaces provides an option to set periodicity separately for the electrolyte andelectrode phase, and to set the potential offset.
• Improved default plots. Vector plots for models not using Porous Electrodedomains now make use of streamline plots with the new arrow feature.
• Updated formulation for the Flux and No Flux nodes included in the mass transportinterfaces.
- The flux relative to the convective flux is prescribed instead of the total flux.
- The new formulation implies that the nodes can be used on a moving meshgeometry without compensating for the boundary velocity.
- Affected interfaces: Transport of Diluted Species: Transport of Diluted Species in
Porous Media, Tertiary Current Distribution, Nernst-Planck; Electroanalysis;
and Electrophoretic Transport.
• Updated equation display for governing equations and boundary conditions in themass transport interfaces. Updated equations are formulated in terms of the flux
relative to the convective flux.
• Updated formulation for the Flux and the No Flux nodes included in the masstransport interfaces.
- The flux relative to the convective flux is prescribed instead of the total flux.
- The new formulation implies that the nodes can be used on a moving meshgeometry without compensating for the boundary velocity.
- Affected interfaces: Transport of Diluted Species, Transport of Diluted Species in
Porous Media, Tertiary Current Distribution, Nernst-Planck; Electroanalysis,
and Electrophoretic Transport.
• Updated equation display for governing equations and boundary conditions in themass transport interfaces. Equations are updated to be formulated in terms of theflux relative to the convective flux.

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New and Updated Models in Version 5.4
The Electrodialysis model has been updated to make use of the new Ion Exchange
Membrane domain feature and the improved Periodic Condition feature in the
Tertiary Current Distribution, Nernst-Planck interface.

Backward Compatibility with Version 5.3a
NO FLUX FORMULATION

The formulation of the No Flux feature has been changed in the Transport of Diluted
Species interface in version 5.4 so that the flux relative to the convective flux is set tozero. The new formulation is used when opening a model from a previous session. In
the previous formulation, the total flux was set to zero.
Affected interfaces: Transport of Diluted Species; Transport of Diluted Species in
Porous Media; Tertiary Current Distribution, Nernst-Planck; Electroanalysis; andElectrophoretic Transport.

74 |CHAPTER 1: RELEASE NOTESE le c t r o de po s i t i on Mod u l e
New Functionality in Version 5.4• A tortuosity option has been added for effective transport parameter correction fordomain nodes modeling transport in porous media. This option is available in thePrimary Current Distribution and Secondary Current Distribution; Tertiary
Current Distribution, Nernst-Planck; Lithium-Ion Battery; Battery with Binary
Electrode; Single Particle Battery; and Electrophoretic Transport interfaces.
• An Equilibrium Potential Handling (Primary Condition) setting has been added to
the Electrode Surface and Porous Electrode Surface nodes. When there are multiple
Electrode Reaction/Porous Electrode Reaction subnodes present, this setting
controls which equilibrium potential will be used in Current Distribution
Initialization studies.
• A new Ion Exchange Membrane domain feature has been added to the Tertiary
Current Distribution, Nernst-Planck interface.
• An improved Ion Exchange Membrane Boundary feature is now available in the
Tertiary Current Distribution, Nernst-Planck interface that supports transport ofmultiple ions across the membrane.
• PARDISO is now the default for the Direct solver in the Current Distribution andBattery interfaces.
• Accurate boundary fluxes have been added to the Electrophoretic Transportinterface.
• A new Fast Irreversible Surface Reaction node has been added to the Tertiary
Current Distribution, Nernst-Planck and Transport of Diluted Species interfaces.
• A new Fast Irreversible Electrode Reaction electrode kinetics expression type has
been added to the Electrode Reaction subnode of the Electrode Surface node in theElectroanalysis and Transport of Diluted Species interfaces. The same feature has
also been added to the Internal Electrode Surface and Thin Electrode Surface
features in the Tertiary Current Distribution, Nernst-Planck interface.
• The Electrostatics interface now supports the Frequency Domain, Perturbation
study step.
• The Electric Potential dependent variable now uses quadratic elements in the
Tertiary Current Distribution, Nernst-Planck interface.

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• A new Heat of Reaction section has been added to the Electrode Reaction andPorous Electrode Reaction nodes in the electrochemistry interfaces. The newsection supports setting the thermoneutral voltage.
• An improved Periodic Condition feature in the Primary Current Distribution;
Secondary Current Distribution; and Tertiary Current Distribution, Nernst-Planckinterfaces provides an option to set periodicity separately for the electrolyte andelectrode phase, and to set the potential offset.
• Improved point/edge (2D/3D) conditions at the intersection between a dissolving(corroding) Deforming Electrode Surface multiphysics node and a Nondeforming
Boundary multiphysics node.
• Improved default plots. Vector plots for models not using Porous Electrodedomains now make use of streamline plots with the new arrow feature.
• Updated formulation for the Flux and No Flux nodes included in the mass transportinterfaces.
- The flux relative to the convective flux is prescribed instead of the total flux.
- The new formulation implies that the nodes can be used on a moving meshgeometry without compensating for the boundary velocity.
- Affected interfaces: Transport of Diluted Species; Transport of Diluted Species in
Porous Media; Tertiary Current Distribution, Nernst-Planck; Electroanalysis;
and Electrophoretic Transport.
• Updated equation display for governing equations and boundary conditions in themass transport interfaces. Updated equations are formulated in terms of the flux
relative to the convective flux.
• Updated formulation for the Flux and the No Flux nodes included in the masstransport interfaces.
- The flux relative to the convective flux is prescribed instead of the total flux.
- The new formulation implies that the nodes can be used on a moving meshgeometry without compensating for the boundary velocity.
- Affected interfaces: Transport of Diluted Species, Transport of Diluted Species in
Porous Media, Tertiary Current Distribution, Nernst-Planck; Electroanalysis,
and Electrophoretic Transport.
• Updated equation display for governing equations and boundary conditions in themass transport interfaces. Equations are updated to be formulated in terms of theflux relative to the convective flux.

76 |CHAPTER 1: RELEASE NOTESNew and Updated Models in Version 5.4
There is a new Pulse Reverse Plating tutorial in the Electrodeposition Application
Library.

Backward Compatibility with Version 5.3a
NO FLUX FORMULATION

The formulation of the No Flux feature has been changed in the Transport of Diluted
Species interface in version 5.4 so that the flux relative to the convective flux is set tozero. The new formulation is used when opening a model from a previous session. In
the previous formulation, the total flux was set to zero.
Affected interfaces: Transport of Diluted Species; Transport of Diluted Species in
Porous Media; Tertiary Current Distribution, Nernst-Planck; Electroanalysis; andElectrophoretic Transport.

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Fatigue Module
New Functionality in Version 5.4
FATIGUE EVALUATION FOR MEMBRANES

Fatigue evaluation is now available also for stresses and strains computed in the
Membrane interface. This can also be used for obtaining more accurate results on theboundaries of solid bodies. In this case a very thin membrane, only used for stressevaluation, is added on top of the solid.
MEAN STRESS CORRECTION

In the Stress-Life method, it is now possible to take mean stress effects into account.
Three methods are available: Goodman, Gerber, and Soderberg.
IMPROVED FATIGUE EVALUATION FOR SHELLSWhen performing fatigue evaluation on shells, it is now possible to directly specify thatthe stresses or strains be taken from either the top or bottom side. The third option is
the same as in previous versions — the through-thickness position is taken from thedefault result location specified in the Shell interface.

Backward Compatibility with Version 5.3
Several of the fatigue laws for low-cycle fatigue are customarily expressed in terms ofnumber of load reversals.
In previous versions, the distinction between number of load reversals to failure andnumber of load cycles to failure has not been clear, neither in the theory sections nor
in result output. In version 5.3a, the result is always in terms of cycles, and the
documentation has been clarified at a number of places.
The affected fatigue models are Basquin, Coffin-Manson, Combined Basquin and CoffinManson, Morrow, Smith-Watson-Topper (SWT), Wang-Brown, and Fatemi-Socie.

78 |CHAPTER 1: RELEASE NOTESGeomechanics Module
New Functionality in Version 5.4
DAMAGE MODELINGFor brittle materials, damage caused by cracking is an important failure mechanism.
The new Damage subnode under Linear Elastic Material makes it possible to incorporate
continuum-based damage models, where the material softens as an effect of theseverity of the loading. Various effective scalar damage models based on equivalentstrain measures (Rankine, Smooth Rankine, Norm of elastic strain tensor, and User
defined) are available. You can also select different rules for the damage evolution:
Linear strain softening, Exponential strain softening, and User defined.
Softening material models are numerically problematic due to strong localization of
the damage. For this reason, you often need to use regularization methods whichsmooth the damage over a finite region. Two such methods are available: Crack band
and Implicit gradient.
The damage functionality is available with both the Geomechanics Module and theNonlinear Structural Materials Module. With the Geomechanics Module, you can also
use the Mazars damage for concrete model, which considers not only tensile cracking
but also compressive failure.
SUCTION IN EXTENDED BARCELONA BASIC MODEL

The suction degree of freedom is no longer available in the Extended Barcelona Basic
Model and has been replaced by a user-defined parameter. The old Initial suction
parameter has been removed.
MULTIPLICATIVE DECOMPOSITION IN NONLINEAR ELASTIC MATERIAL

Even though the Nonlinear Elastic Material is mainly intended for small strains, it canalso be used under geometric nonlinearity. The removal of inelastic strains from thetotal strains is now done using multiplicative decomposition, just as for other materials.
By using the check box Additive strain decomposition, you can retrieve the formulation
previously used.

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BURGERS VISCOELASTIC MODEL

A built-in viscoelastic model has been added: the Burgers model. As with the otherviscoelastic models, it is accessed by adding a Viscoelasticity subnode under the
Nonlinear Elastic Material.

New Models in Version 5.4
SLOPE STABILITY IN A DAM EMBANKMENTThis example shows how to run a slope stability analysis in a dam embankment,
including the pore pressure effect. The fluid transport in the porous soil is describedby Darcy’s law, and an elastoplastic analysis is carried out with the Mohr-Coulomb
model. The material properties are parameterized with respect to the factor of safety
using the shear reduction technique.
BRITTLE DAMAGE IN UNIAXIAL TENSIONIn this tutorial model, different methods for modeling brittle damage are compared ina uniaxially loaded bar. The new Damage feature is used. The localization of thedeformation during fracture is studied using different discretization orders andregularization methods.
CRACKING OF A NOTCHED BEAM

In this example, two models for brittle damage are used to evaluate the fracture of anotched concrete beam subjected to three-point bending. The new Damage feature isused. The results are compared with experimental data.
WETTING AND DRYING PATHS FOR PARTIALLY SATURATED SOIL WITH
THE EXTENDED BARCELONA BASIC SOIL MODEL

Experiments on dry and wet soil samples are performed to understand their behavior
under different loading conditions. In this example, the Extended Barcelona Basic(BBMx) soil model is used to simulate the wetting and drying paths in partiallysaturated soil samples under cyclic loading.

80 |CHAPTER 1: RELEASE NOTESHe a t T r a ns f e r Mod u l e
New and Improved Functionality in Version 5.4
EXTENDED CAPABILITIES FOR HEAT TRANSFER IN THIN STRUCTURES

The features and interfaces for the modeling of heat transfer in thin structures havebeen completely redesigned to take advantage of the new Layered Material
functionality. Layered materials are defined on boundaries but correspond to 3D
materials with one or multiple layers. They contain information regarding theircomposition and the thickness of their layers. It is possible to preview the layeredmaterial structure to define properties and heat loads or constraints layer by layer.
Additionally, the functionality offers a postprocessing tool to analyze and visualize thesolution as a 3D structure.
In the Heat Transfer interface, the Thin Layer, Thin Film, and Fracture features now
support layered materials. Once a Layered material has been selected in the Layer
Selection section, the feature is applicable on the boundaries corresponding to theselected layered material. Subfeatures are available for the definition of heat fluxes, heatsources, temperature constraints, and surface-to-ambient radiation.
The Heat Transfer in Shells, Heat Transfer in Films, and Heat Transfer in Fracturesinterfaces, found under the Heat Transfer>Thin Structures branch, contain features forthe modeling of heat transfer by conduction and convection in layered materials. The
Solid, Fluid, and Porous Medium boundary features solve the energy equation in eachlayer, either with a general formulation or a lumped model for thermally thin orthermally thick structures. The Heat Source and Heat Source, Interface features accountfor heat sources inside the layers and between them. Other edge and boundaryinterface features are also available to define heat fluxes, temperature constraints, andsurface-to-ambient radiation at layer edges and interfaces between layers.
Multiphysics couplings are also supported on layered structures: the Electromagnetic
Heating, Layered Shell and Thermoelectric Effect, Layered Shell couplings can be added

on boundaries where either a Heat Transfer interface with the Thin Layer, Thin Film, or
Fracture features or a Heat Transfer in Shells interface is applicable together with an
Electric Currents, Layered Shells interface.

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SURFACE-TO-SURFACE RADIATION WITH SPECULAR REFLECTION AND
TRANSMISSION

A new algorithm, the ray shooting method, is available in the Surface-to-Surface
Radiation interface for view factor computation. It handles mixed diffuse-specularreflection on surfaces as well as transmission in semitransparent surfaces. Althoughrough surfaces reflect incident rays in all direction regardless of the incident direction
and are well-modeled by diffuse surfaces, very smooth surfaces reflect the incident ray
according to the law of reflection and should be modeled as specular.
By selecting the Ray shooting method in the Surface-to-surface radiation method list, it
makes the new Opaque Surface feature available to model mixed diffuse-specularreflection accurately and realistically for a wide range of surfaces. When some layers are
not fully opaque and transmit a fraction of the incident irradiation, the new SemiTransparent Surface feature can be used. This is useful, for example, to model windows
made of glass that reflect and absorb a fraction of the sun radiation and transmit therest. The feature provides settings for the surface emissivity, reflectivity, andtransmissivity.
EXTENDED CAPABILITIES FOR SURFACE-TO-SURFACE RADIATION WITH
WAVELENGTH-DEPENDENT MATERIAL PROPERTIESThe Surface-to-Surface Radiation physics interface now supports an arbitrary numberof subdivisions of the spectral domain. The graphical user interfaces of all radiation
features; namely, Diffuse Surface, Diffuse Mirror, Prescribed Radiosity, Opacity, andExternal Radiation Source, have been reorganized to specify the material properties anduser inputs in a more compact way. The surface emissivity, for example, can beprovided either by giving its value for each spectral band, or by entering a wavelengthdependent expression, with rad.lambda giving access to the wavelength variable. The
same improvements also apply to the new wavelength-dependent material properties
and user inputs required by the new specular radiation functionalities; namely, surface
reflectivity, surface transmissivity, and critical angle.
EXTENDED CAPABILITIES FOR RADIATION IN PARTICIPATING MEDIA

Several improvements have been implemented for the modeling of radiation inparticipating media. A new option is available to define the radiation scattering, theHenyey-Greenstein phase function. It offers an interesting compromise between
complexity and accuracy to represent scattering due to particles in a participating
medium. In order to simplify the phase definition, it is now possible to normalize thephase function for Linear anisotropic and Polynomial anisotropic scattering types.

82 |CHAPTER 1: RELEASE NOTESIn addition, several new quadrature sets have been added for the discrete ordinates
method (DOM) in the Radiation in Participating Media and Radiation in AbsorbingScattering Media interfaces. In addition to the Level Symmetric Even set, two additional
SN approximations are available: Level Symmetric Hybrid and Equal Weight Odd. These
sets differ in the moment conditions they satisfy, and introduce 8 to 168 discrete
ordinates, depending on the selected order. A TN approximation, the Quasi-uniform
weight approximation, is also available. It discretizes the angular space by using areference octahedron with 8 triangular faces, further discretized in function of theorder of the method, to produce from 8 to 512 discrete ordinates. The choice of thequadrature set and order depends on the accuracy needs and the available
computational resources.
RADIATION IN ABSORBING-SCATTERING MEDIA INTERFACEThe new Radiation in Absorbing-Scattering Media physics interface can be foundunder the Radiation group of the Heat Transfer branch. It provides features to model
the propagation, absorption, and scattering of radiation in a semitransparent medium.
In particular, it is well-suited for the modeling of light diffusion in a nonemitting
medium.
Like the Radiation in Participating Media interface, it solves the Radiative Transfer
Equation, but with no emission term. Therefore, the two interfaces share the same
discretization methods (P1 approximation and Discrete Ordinates Method) and options
for the definition of scattering.
The Absorbing-Scattering Medium domain node defines the absorption and scattering
properties and the radiative heat source due to absorption. On boundaries, the Incident
Intensity node allows you to specify the radiative intensity along incident directions,and the Opaque Surface node specifies a wall that absorbs all the radiative intensity,
producing heat.
REFACTORING OF HEAT TRANSFER WITH RADIATION FUNCTIONALITIESINTO MULTIPHYSICS COUPLINGSThe Surface-to-surface radiation and Radiation in participating media check boxes,
previously found under the Physical Model section of the Heat Transfer interface, havebeen removed. This means that the Heat Transfer interface does not support thesurface-to-surface radiation features and radiation in participating media features
anymore, with the exception of the Surface-to-Ambient Radiation feature. In particular,
the Diffuse Surface, Diffuse Mirror, Prescribed Radiosity, Opacity, and External Radiation
Source features are now available exclusively in the Surface-to-Surface Radiationinterface. The Radiation in Participating Media, Opaque Surface, Incident Intensity, andHEAT TRANSFER MODULE|

83

Continuity on Interior Boundary features are now available exclusively in the Radiationin Participating Media interface.
To achieve the modeling of heat transfer with radiation, the following multiphysics
predefined interfaces and couplings have been added:• The new Heat Transfer with Surface-to-Surface Radiation predefined multiphysics
interface, available under the Heat Transfer>Radiation branch, automatically adds a
Heat Transfer interface and a Surface-to-Surface Radiation interface, coupledthrough the Heat Transfer with Surface-to-Surface Radiation multiphysics coupling.
• The new Heat Transfer with Radiation in Participating Media predefined
multiphysics interface, available under the Heat Transfer>Radiation branch,
automatically adds a Heat Transfer interface and a Radiation in Participating Media
interface, coupled through the Heat Transfer with Radiation in Participating Media
multiphysics coupling.
• The new Heat Transfer with Radiation in Absorbing-Scattering Media multiphysics
interface, available under the Heat Transfer>Radiation branch, automatically adds a
Heat Transfer interface and a Radiation in Absorbing-Scattering Media interface,coupled through the Heat Transfer with Radiation in Absorbing-Scattering Media
multiphysics coupling.
• The new Heat Transfer with Radiative Beam in Absorbing Media multiphysics
interface, available under the Heat Transfer>Radiation branch, automatically adds a
Heat Transfer interface and a Radiative Beam in Absorbing Media interface, coupledthrough the Heat Transfer with Radiative Beam in Absorbing Media multiphysics
coupling.
REFACTORING OF FUNCTIONALITIES INTO SUBFEATURES

In order to achieve a better clarity and usability of the user interface, the following
subfeatures have been added. They provide the settings corresponding to a particularconfiguration of the parent feature:• The new Convectively Enhanced Conductivity subfeature is available under the Fluidand Moist Air nodes. It provides the settings previously available under the Equivalent
Conductivity for Convection section of the Fluid and Moist Air nodes, to account for
convective heat flux by enhancing the fluid thermal conductivity according to the
Nusselt number.
• The new Thermal Damage subfeature is available under the Biological Tissue node. It
provides the settings previously available under the Damaged Tissue section of the
Biological Tissue node, for the definition of the Transformation model.

84 |CHAPTER 1: RELEASE NOTESIn addition, the Rosseland approximation for radiative heat transfer in media with highoptical thickness is now handled by the new Optically Thick Participating Medium
subnode, available under most of the domain features of the Heat Transfer interface.
It provides the settings to account for the radiative heat source by enhancing thethermal conductivity. Although it is used to model radiation, it is conceptually different
from the Participating Medium feature that solves for additional variables (radiative
intensity or incident radiation) to compute the radiative heating. It replaces theRosseland approximation option of the Radiation discretization method list previously
available under the Participating Media Settings section.
Finally, the new Phase Change Material subfeature replaces the Phase Change Materialfeature, and extends its capabilities to solids and porous media. It is available under the
Solid, Fluid, and Porous Medium nodes, and provides the same settings as the obsoletefeature, to specify the properties of a phase change material according to the apparent
heat capacity formulation. When added under the Solid node, a single density should
be defined for all phases to ensure mass conservation on the material frame.
VOLUME REFERENCE TEMPERATURE MODEL INPUTThe features defined on the material frame, with an input field for the density, have a
new model input: the Volume reference temperature. This is the temperature for theevaluation of the density in the reference geometry, which should match the geometry
in the material frame. By default, this model input is set to the Common model input
variable, minput.Tempref. This ensures mass conservation during the simulation.
This concerns the following features: Solid, Porous Medium, Biological Tissue, Building
Material, Shape Memory Alloy, Thin Layer, and Fracture in the Heat Transfer interface,and Solid, Porous Medium in the Heat Transfer in Shells interface.
MISCELLANEOUS• The new Heat and Moisture Flow multiphysics interfaces are available under the Heat
Transfer>Heat and Moisture Transport branch to model coupled heat transfer andmoisture transport in air by laminar and turbulent flows. The different interfaces
couple the laminar and turbulent versions of the Single-Phase Flow interfaces with
the Heat Transfer in Moist Air and Moisture Transport in Air interfaces. The Heatand Moisture, Moisture Flow, and Nonisothermal Flow multiphysics coupling nodes
handle turbulent mixing and heat and moisture wall functions for turbulent flows aswell as account for the temperature and moisture content dependency of material
properties in the fluid flow equations in air.
• The new Heat Transfer in Solids and Fluids interface, available in the Model Wizard
under the Heat Transfer branch, replaces the Heat Transfer interface that was

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85

previously available uniquely through the addition of the Conjugate Heat Transfer
multiphysics interface. A Solid feature is active by default on all domains, and a Fluidfeature has an empty selection by default. Similarly to the Heat Transfer in Fluids
interface, its default discretization order is 1.
• The Thermal Insulation feature is now available on interior boundaries. It ensuresthat no heat transfer occurs at the boundaries this feature is applied on, henceinterrupting the default temperature continuity condition. Note that the default
Thermal Insulation feature is still not applicable on interior boundaries.
• A new Ambient Thermal Properties node is available under the Definitions node. It
contains the Ambient Settings section that was previously available in the Heat
Transfer interface. Several Ambient Thermal Properties nodes may be added in asingle model. The ambient variables defined by this node remain available from thephysics features.
• In the External Radiation Source global feature, it is now possible to define the Solar
position from a Weather station setting made in an Ambient Thermal Properties node
under Definitions. When an Ambient Thermal Properties node is added with Ambient
data set to Meteorological data (ASHRAE 2013) or Meteorological data (ASHRAE 2017),
this node can be selected from the Ambient data list in the External Radiation Source
feature.
• The user input for the Reference temperature, used in the incompressible flow
formulation for nonisothermal flows, and for the computation of the reference
enthalpy in the heat transfer equation, has been moved from the Physical Modelsection of the Single-Phase Flow interface to the Physical Model section of the Heat
Transfer interface. In addition, its default value has changed from 298.15 K to
293.15 K.
• Additional surface plots are generated by default in the Temperature plot group of
3D models when the Thermal Contact feature is active on some boundaries, todisplay the temperatures on the upside and downside of the slit defined by thefeature on these boundaries.
• In the Symmetry for Surface-to-Surface Radiation global feature, it is now possible todefine the symmetry planes by selecting points manually from the Graphics window,
instead of providing their coordinates. The Point selection option can be selectedfrom the Selection method list.
• The default presmoother and postsmoother in the GMRES iterative solver havechanged from SOR line to SCGS when the Nonisothermal Flow coupling is used. In
addition, in 3D models with a Local Thermal Non-Equilibrium coupling, the default

86 |CHAPTER 1: RELEASE NOTESSegregated node has been replaced by a Fully Coupled node, in order to solve for thetwo (solid and fluid) temperatures in a single step.
• In 1D models, the default value of the Cross sectional perimeter has been changed
to 2*(sqrt(pi*ht.Ac)) in the Physical Model section, for consistency with thedefault Cross sectional area.
• The definitions of the sensible enthalpy (ht.DeltaH) and total energy flux
(ht.Teflux) postprocessing variables have been improved in porous media and thin
structures.

New Applications in Version 5.4
ISOTHERMAL BOX

This new tutorial model shows how to model an isothermal box used to transport
refrigerated medical materials. The goal is to keep the material between a restricted
temperature range from 2°C to 8°C for 24 hours. Ice-to-water phase change plays acrucial role. Eutectic plates containing ice act as energy storage by absorbing theexterior warmth during the melting process that occurs at 0°C, hence maintaining thecontent at low temperature. The simulation is performed for 72 hours so that thetemperature evolution can also be observed after the cooling ice packages havecompletely melted.
ACTION ON STRUCTURES EXPOSED TO FIRE

Five new tutorial models contain verification examples from the European Standard
EN 1991-1-2:2010-12, Eurocode 1: Actions on structures — Part 1–2: General
actions: Actions on structures exposed to fire.
• The Action on Structures Exposed to Fire — Cooling Process tutorial addresses thefirst verification example of the norm. A transient cooling process due to convection
is modeled. The tutorial verifies that the numerical results obtained with COMSOLMultiphysics are within the validity ranges specified in the norm.
• The Action on Structures Exposed to Fire — Heating Process tutorial addresses thesecond verification example of the norm. It describes a heating process due toconvection and radiation using a temperature-dependent thermal conductivity. The
tutorial verifies that the numerical results obtained with COMSOL Multiphysics arewithin the validity ranges specified in the norm.
• The Action on Structures Exposed to Fire — Heat Transfer in Multiple Layers
tutorial addresses the third verification example of the norm. It describes a heating

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87

process through layers using a temperature-dependent thermal conductivity. The
tutorial computes heat transfer through layers with different material properties.
• The Action on Structures Exposed to Fire — Thermal Elongation tutorial
addresses the fourth verification example of the norm. The tutorial verifies that thecalculated elongation matches the expected values.
• The Action on Structures Exposed to Fire — Thermal Stress in a Beam tutorial
addresses the seventh verification example of the norm. It describes the nonlinear
mechanical behavior of a beam that is exposed to a temperature gradient. The
numerical results obtained with COMSOL Multiphysics are compared with thereference values specified in the norm.

Updated Applications in Version 5.4
USE OF THE NEW INTERFACES AND FEATURES FOR LAYERED MATERIALSThe following tutorials have been updated to use the new Thin Layer feature, applicableon layered materials: Fluid-Structure Interaction in Aluminum Extrusion, DoublePipe Heat Exchanger, Finned Pipe, Forced Convection Cooling of an Enclosure with
Fan and Grille, Heating Circuit, Sun's Radiation Effect on Two Coolers Placed
Under a Parasol, Shell-and-Tube Heat Exchanger, Heat Transfer in a SurfaceMount Package for a Silicon Chip, Natural Convection Cooling of a Vacuum Flask,
Disk-Stack Heat Sink, Composite Thermal Barrier, and Silica Glass Block Coatedwith a Copper Layer.
The following tutorials have been updated to use the new Heat Transfer in Shells
interface, applicable to layered materials: Disk-Stack Heat Sink, Shell Conduction.
USE OF THE NEW HEAT TRANSFER WITH SURFACE-TO-SURFACERADIATION INTERFACE

Several tutorials have been updated to use the new Heat Transfer with Surface-toSurface Radiation multiphysics interface: Electronic Chip Cooling, Free Convection
in a Light Bulb, Flash Method, Radiation in a Cavity, Sun's Radiation Effect on
Two Coolers Placed Under a Parasol, Rapid Thermal Annealing, and ThermoPhoto-Voltaic Cell.
USE OF THE NEW HEAT TRANSFER WITH RADIATION IN PARTICIPATINGMEDIA INTERFACEThe Radiative Cooling of a Glass Plate tutorial has been updated to use the new Heat
Transfer with Radiation in Participating Media multiphysics interface.

88 |CHAPTER 1: RELEASE NOTESUSE OF THE NEW HEAT TRANSFER IN SOLIDS AND FLUIDS INTERFACE

Several tutorials have been updated to use the new Heat Transfer in Solids and Fluids
interface, including Electronic Chip Cooling, Free Convection in a Light Bulb, Tin
Melting Front, Finned Pipe, Thermal Performances of Windows, and Forced
Convection Cooling of an Enclosure with Fan and Grille. Note that when the Heat
Transfer in Solids interface was used in these tutorials, the discretization order waschanged from quadratic to linear by using the new interface. Therefore, some smallchanges in the results can be observed. This is the case for the Thermal Performancesof Windows tutorial in particular.
USE OF THE NEW MOVING MESH NODE UNDER DEFINITIONSThe Fluid Damper tutorial has been updated to use the Moving Mesh node under
Definitions instead of the Moving Mesh interface. In addition, it has been updated byusing the Incompressible flow option in the Laminar Flow interface, as the density
defined in the material is not temperature dependent, by setting the initial time to 0
for the time-dependent study, and by improving the settings for postprocessing.
The Dynamic Wall Heat Exchanger tutorial has been updated to use the Moving Meshnode under Definitions instead of the Moving Mesh interface.

Backward Compatibility with Version 5.3a
• The Heat Transfer in Thin Shells (htsh), Heat Transfer in Thin Films (htsh), andHeat Transfer in Fractures (htsh) interfaces that do not support the Layered Material
functionality are now obsolete. When opening a model created in version 5.3a or
earlier in the GUI, these interfaces are not migrated. They should be manuallyreplaced by the corresponding Heat Transfer in Shells (htlsh), Heat Transfer inFilms (htlsh), and Heat Transfer in Fractures (htlsh) interfaces that support theLayered Material functionality. The Thin Layer, Thin Film, and Fracture features are
replaced by the Solid, Fluid, and Porous Medium features in the new interfaces.
• The Thin Layer, Thin Film, and Fracture features (and their subfeatures) that do notsupport the Layered Material functionality are now obsolete. When opening a model
created in version 5.3a or earlier in the COMSOL Desktop, these features are notmigrated. They should be manually replaced by the corresponding features that
support the Layered Material functionality. Note that the pair features for thin
structures are no longer available for layered materials. The obsolete Thin Layer, Thin
Film, and Fracture features remain available through the COMSOL API so thatexisting scripts remain compatible. However, it is recommended to update theHEAT TRANSFER MODULE|

89

scripts to use the new features as the obsolete features will be discontinued in futureversions.
• The Surface-to-surface radiation check box has been removed from the Physical Modelsection of the Heat Transfer interface. As of Version 5.4, surface-to-surface radiation
models should use the Surface-to-Surface Radiation physics interface coupled witha Heat Transfer domain physics interface via the Heat Transfer with Surface-toSurface Radiation multiphysics coupling feature. The Heat Transfer interface does
not support the Diffuse Surface, Diffuse Mirror, Prescribed Radiosity, Opacity, andExternal Radiation Source features anymore. Models built prior to v5.3a using
surface-to-surface radiation features formerly available in the Heat Transfer
interfaces will mark these features as obsolete. Support for features marked as
obsolete is not ensured in future versions, thus it is strongly recommended totransfer all these features to a Surface-to-Surface Radiation physics interface and use
a Heat Transfer with Surface-to-Surface Radiation multiphysics coupling feature.
• The Radiation in participating media check box has been removed from the PhysicalModel section of the Heat Transfer interface. From Version 5.4, radiation inparticipating media models should use the Radiation in Participating Media physics
interface coupled with a Heat Transfer physics interface via the Heat Transfer with
Radiation in Participating Media multiphysics coupling feature. The Heat Transfer
interface does not support the Radiation in Participating Media, Opaque Surface,
Incident Intensity, and Continuity on Interior Boundary features anymore. Models
built prior to v5.3a using radiation features formerly available in the Heat Transfer
interfaces will mark these features as obsolete. Support for features marked as
obsolete is not ensured in future versions, thus it is strongly recommended totransfer all these features to a Radiation in Participating Media physics interface anduse a Heat Transfer with Radiation in Participating Media multiphysics coupling
feature.
• The Ambient Settings section has been removed from the Heat Transfer interface.
When opening a model created in version 5.3a or earlier in the COMSOL Desktop,
in which some of the input fields of this section have been edited, an Ambient
Thermal Properties node is automatically created under Definitions with the samesettings. If some ambient variables have been selected in features, the feature inputs
are updated as well.
• The Phase Change Material feature has been replaced by the Phase Change Material
subfeature. When opening a model created in version 5.3a or earlier in the
COMSOL Desktop, a Fluid node with the Phase Change Material subfeature is

90 |CHAPTER 1: RELEASE NOTESautomatically created in place of the obsolete feature. This node is labeled Phase
Change Material in the model.
• The Damaged Tissue section has been removed from the Biological Tissue feature.
When opening a model created in version 5.3a or earlier in the COMSOL Desktop,
in which the Include damage integral analysis check box of this section has been
selected, a Thermal Damage node is automatically added under Biological Tissue withthe same settings. Note that for the Temperature threshold option, it is no longer
possible to perform simultaneous hyperthermia and cryogenic analysis. The
Hyperthermia analysis option is therefore selected by default when opening themodel.
• The Rosseland approximation option, which was available in the Radiation
discretization method list of the Radiation in Participating Media feature, has been
removed. When opening a model created in version 5.3a or earlier in the COMSOLDesktop, in which this option has been selected, an Optically Thick Participating
Medium subnode is automatically created under the active domain node.
• The Medium Properties feature has been renamed Absorbing Medium in the Radiative
Beam in Absorbing Medium interface, with identical settings and modeling. Whenopening a model created in version 5.3a or earlier in the COMSOL Desktop, an
Absorbing Medium feature is automatically created in place of the obsolete feature.
This node is still labeled Medium Properties in the model.
• The Radiation in Participating Media feature has been renamed Participating Medium
in the Radiative Beam in Absorbing Medium interface. When opening a model
created in version 5.3a or earlier in the COMSOL Desktop, a Participating Mediumfeature is automatically created in place of the obsolete feature. This node is stilllabeled Radiation in Participating Media in the model.
• The Change Thickness and Change Cross Section features have been renamed Thickness
and Cross Section, respectively. When opening a model created in version 5.3a or
earlier in the COMSOL Desktop, these features are not migrated. They should be
manually replaced by the new features.

Backward Compatibility with Version 5.3• The Electromagnetic Heat Source and Boundary Electromagnetic Heat Source coupling
features are now obsolete. They have been merged into a single Electromagnetic
Heating coupling feature. When opening a model created in version 5.3 or earlier in
the COMSOL Desktop, the Electromagnetic Heat Source and Boundary
Electromagnetic Heat Source features are automatically migrated to Electromagnetic

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Heating features with selections (respectively a domain and a boundary selection)that match the selections of the migrated features. The obsolete Electromagnetic
Heat Source and Boundary Electromagnetic Heat Source features remain available

through the COMSOL API so that existing scripts remain compatible. However, it
is recommended to update the scripts to use the new Electromagnetic Heating featureas the obsolete feature will be discontinued in future versions. Note thattemperature coupling is enforced in the 5.3a version of the Electromagnetic Heating
coupling feature.
• The Thermoelectric Effect and Boundary Thermoelectric Effect coupling features havebeen merged into a new Thermoelectric Effect coupling feature. When opening amodel created in version 5.3 or earlier in the COMSOL Desktop, the Thermoelectric
Effect and Boundary Thermoelectric Effect features are automatically migrated to the
new Thermoelectric Effect feature with selections (respectively a domain and aboundary selection) that match the selections of the migrated features. The obsolete
Thermoelectric Effect and Boundary Thermoelectric Effect features remain available
through the COMSOL API so that existing scripts remain compatible. However, it
is recommended to update the scripts to use the new Thermoelectric Effect feature as
the obsolete feature will be discontinued in the future. Note that temperature
coupling is enforced in the 5.3a version of the Thermoelectric Effect coupling feature.
• The Inflow Heat Flux boundary condition is now obsolete. It can be replaced by the
new Inflow boundary condition and the Boundary Heat Source condition.
• The Enable conversions between material and spatial frame check box, displayed in
the Advanced Settings section of the Heat Transfer interfaces when the modelcomponent supports moving mesh, has been removed. This means that conversion
between material and spatial frames is always effective when these frames differ.
• The Energy absorption option has been renamed Arrhenius kinetics in theTransformation model list of the Irreversible Transformation and Biological Tissue
nodes.
• The Convective moisture flux option has been renamed Convective moisture flux,pressures difference in the Moisture Flux node.
• The rhoInt, CpInt, and gammaInt variables, defined by the Fluid domain feature,
have been removed.
• The q_evap variable, defined by the Moist Surface and Wet Surface boundary nodes,
has been replaced by the q_evaptot variable.
The General option for Thin film model has been removed from the Thin Film fallback
node.

92 |

CHAPTER 1: RELEASE NOTESBackward Compatibility with Version 5.2a
The obsolete features Convective Heat Flux and Out-of-plane Convective Heat Flux are
removed in Version 5.3. These were marked as obsolete with a warning message since
Version 5.0. These features will be removed from your model when opening in Version
5.3. Use instead the corresponding Heat flux and Out-of-Plane Heat Flux features, withthe option Convective heat flux. The variables ht.chflux, ht.chflux_u,
ht.chflux_d, and ht.chflux_z defined by these features have been also removed
from equation view and postprocessing variables menu.
The new default option in Thin Moisture Barrier feature is Vapor barrier material
properties, and the Moisture barrier material properties option has been removed. Whenloading a MPH file that was created before version 5.3 this latter option will be cleared,
and the corresponding user inputs used to define the Moisture transfer coefficient
directly. However, for the API, it will be necessary to update the code with an existing
option name.
In the Equivalent Conductivity for Convection section of the Fluid node, the new
Automatic option for Temperature difference has become the default option. Whenloading a MPH file that was created before version 5.3, the User defined option will be
set automatically with the previous value. However, for the API, it will be necessary to
update the code to set the User Defined option.

Backward Compatibility with Version 5.2
Several enhancements or bug fixes may require an update of the existing applications
or induce a change in the results. Here is the list of the changes:• When Solar position is selected in External Radiation Source, the new option Update
time from solver is selected by default. When loading an MPH file that was created
before version 5.2a this option will be cleared. However, for the API, for timedependent studies, it will be necessary to update the code to get the same behavior
as in previous versions. In most cases, removing the t term in the Second field is thebest option. Alternatively, clearing the Update time from solver option will ensurethat the same behavior as before is obtained.
• The crosswind stabilization of the heat transfer and fluid flow interfaces has been
updated. In general, the update reduces the smoothing induced by the stabilizationcompared to previous version. In addition, when you use the Nonisothermal Flow
multiphysics coupling and the fluid is defined as incompressible, the uncoupled
versions of the streamlines and crosswind stabilization are used.

HEAT TRANSFER MODULE|

93• Since Pair Thin Film and Pair Fracture are now pair features, their selection needs tobe redefined.
• The definition of the ht.feature.fc(RH.T,pA) function when Moist air fluid type
is used in Fluid feature has been corrected. This change can affect the results insimulations where it is used.
• The frame support has been enhanced to support moving mesh combined with
deformed geometry in the same component.
• The Prescribed Radiosity feature has been updated so that it no longer ignores theTemperature model input.
• In surface-to-surface boundary features, the ambient temperature definition has
been fixed when the Opacity Controlled and Defined ambient temperature on each side
options are used simultaneously.

Backward Compatibility with Version 5.1
CHANGES IN VARIABLE NAMESThe names of the heat capacity variables have changed in several features forconsistency:• In the Bioheat feature, ht.cb has become ht.cp_b.
• In the Thin Layer feature, ht.cs has become ht.cp_s.
• In the Thin Rod feature, ht.cl has become ht.cp_l.
• In the Thin Layered Shell feature, htsh.cs1 has become htsh.cp_s1, and so on.
• In the Heat Transfer in Porous Media feature, ht.c_pp has become ht.cp_p,
ht.c_pp1 has become ht.cp_p1, and so on.
• In the Immobile Fluids feature, ht.c_pg1 has become ht.cp_g1, and so on.
• In the Fracture feature, ht.c_pfr has become ht.cp_fr.
The names of the thermal resistance and absolute thermal resistance variables havechanged in the Isothermal Domain Interface feature:• ht.idi1.Rs has become ht.idi1.R_t• ht.idi1.Rsth has become ht.idi1.R_tth
The name of the fluid viscosity variable has changed in the Local Thermal NonEquilibrium multiphysics coupling: ltne1.mu_f has become ltne1.mu.

94 |CHAPTER 1: RELEASE NOTESBackward Compatibility with Version 5.0
OBSOLETE FEATURES

A number of features are now obsolete because they have been merged or replaced bya more general features. However, when models from COMSOL 5.0 or before containthese features, some of the obsolete features are visible in version 5.2a with a warning
sign notifying that the feature is now obsolete (see Table 1-1). Some features havebeen completely removed (see Table 1-2). A model containing any of them can be
opened in 5.2a, but the feature will be missing.
Updating the models is recommended. Use the new feature and remove the obsoletefeature to make sure that the model will remain compatible with future versions of
COMSOL Multiphysics.
The table below summarizes the changes:
TABLE 1-1: OBSOLETE FEATURES THAT ARE OBSOLETE BUT THAN CAN BE LOADED IN 5.1
OBSOLETE FEATURE

REPLACE IN 5.2A BY

Convective Heat Flux

Heat Flux with the Convective heat flux option

selected
Surface-to-Ambient Radiation

Diffuse Surface with Include surface-to-surface
radiation deselected

Surface-to-Surface Radiation

Diffuse Surface with Include surface-to-surface
radiation selected

Highly Conductive Layer

Thin Layer with Layer type set to Conductive

Thin Thermally Resistive Layer

Thin Layer with Layer type set to Resistive

TABLE 1-2: OBSOLETE FEATURES THAT ARE NO LONGER AVAILABLEOBSOLETE FEATURE

REPLACE IN 5.2A BY

Infinite Element

Infinite Element is no longer defined in thephysics interface. Infinite elements are definedin the Definitions section instead.

Electrochemical Heat flux

Boundary Heat Source

Reaction Heat Flux

Boundary Heat Source

Heat Transfer in Participating
Media

Heat Transfer in Solids contributing to
Radiation in Participating Media

Porous Matrix

Heat Transfer in Porous Media

Note that it is not possible to add any of the obsolete features from the COMSOLDesktop in version 5.2a. Only the new features are available.

HEAT TRANSFER MODULE|

95

OBSOLETE POSTPROCESSING VARIABLES DELETED IN 5.1

List of deleted postprocessing variables: ndflux_acc, ndflux_acc_u, ndflux_acc_d,
ntflux_acc, ntflux_acc_u, ntflux_acc_d, nteflux_acc, nteflux_acc_u,
nteflux_acc_d, qout, qout_u, qout_d, qin, qin_u, qin_d, qw, qw_u, and qw_d.
CHANGES IN VARIABLE NAMES

The variable ht.Tvar, used for nonisothermal flow wall functions, becomes a fully
scoped variable in the following features:• Heat Flux (ht.hf1.Tvar), Line Heat flux, Point Heat flux, and Out of plane heat flux.
• Heat Source (ht.hs1.Tvar), Boundary heat source, Line heat source, and Point heatsource.
• Diffuse Surface (ht.ds1.Tvar).
The fully scoped variables Ptot, Pbtot, Pltot, and Pstot become P0, Pb, Pl, and Ps,
respectively, in the following features:• Heat Flux
• Inflow Heat Flux
• Line Heat Flux
• Heat Source• Boundary Heat Source• Line Heat Source• Line Heat Source (Thin Rod subfeature)• Line Heat Source on Axis
• Layer Heat Source (Thin Layer subfeature)
In the Thermal Contact feature:• Qfric, QfricPow, and Qrate become Qb, Pb, and Qbpart, respectively• Qfric0, Qrate0, Econtact0, hrad0, hgap0, and hconstr0 are removed andmigrated to existing variables Qb, Qbpart, Econtact, hrad, hgap, and hconstr,
respectively, in old models.
The Change Effective Thickness feature from the Heat Transfer in Thin Shells interface
merges htsh.de into the existing variable htsh.ds.
The Heat Transfer in Thin Shells interface also merges the property de and variable
htsh.de into existing property ds and variable htsh.ds. An API command such as

96 |CHAPTER 1: RELEASE NOTES

model.physics("htsh").prop("de").set("de", [...]) now does not have any

effect.

Backward Compatibility with Version 4.4
OUT-OF-PLANE HEAT TRANSFER UPDATEThe out-of-plane heat transfer property, which was available in 2D and 1D geometries,
has been removed as of COMSOL Multiphysics 5.0. Now, all geometries are
considered 3D geometries and thickness or area parameters are always available.

API Users
With the Overall heat transfer rate option (previously named Total power or Total heatflux), the thickness parameters (dz_entr and Ac_input) have been removed for thefollowing features:• Heat Source• Heat Flux
• Boundary Heat Source• Layer Heat Source• Inflow Heat Flux
Compatibility with previous code is maintained for most of the cases. However, three
configurations require manual updates of the code:• If you specified the thickness parameter twice (there were two instances of specifying
the parameter).
• If you first specified the thickness and in a second command the total power value.
• If you first specified the thickness and then activated the out-of-plane heat transfer
option.
For these 3 cases, you need to rewrite this part of the Java® code by doing thefollowing. For a heat source example (2D and 1D axisymmetric geometries):
Ptot_50 = Ptot_44_value*ht.d/dz_entr_44_value,
where Ptot_44_value is the total power value used in previous versions, Ptot_50 is
the total power value used since COMSOL Multiphysics 5.0, and dz_entr_44_value
is the value used in previous versions.
In 1D geometries, the following update should be performed: Ptot_50 =Ptot_44_value*ht.d/Ac_input_44_value ,where Ac_input_44_value is the value used in previous versions.

HEAT TRANSFER MODULE|

97

Flux Variables
The flux variables are always given in W/m² (also for 2D or 1D geometries). To obtainthe corresponding flux variables in W/m on a boundary in 2D, for example, the flux
variables have to be multiplied by the thickness ht.d.
The following variables have been updated following this convention:• Conductive heat flux, ht.dflux• Convective heat flux , ht.cflux• Translational heat flux, ht.trlflux• Total energy flux, ht.teflux• Total heat flux, ht.tflux• Boundary convective heat flux, ht.chflux• Radiative heat flux, ht.rflux
All flux variables now have the following sign convention: positive heat flux
corresponds to heating, whereas negative heat flux corresponds to cooling. The
variables chflux and rflux may have opposite signs compared to previous versions,depending on the context where they are defined.
INFLOW HEAT FLUX IS ONLY APPLICABLE ON NON-SOLID DOMAINS

The Inflow Heat Flux feature is no longer applicable on boundaries adjacent to thefollowing domain features: Heat Transfer in Solids, Biological Tissue, and Isothermal
Domain. This restriction avoids ill-posed configurations due to the null velocity field inthese features. This may change model results if this boundary condition waspreviously applied to a boundary adjacent to a nonfluid domain.
HEAT TRANSFER WITH PHASE CHANGE NOW USES A VOLUMETRICFORMULATION

The variables ht.thetai now represent volume fractions (they were mass fractions
before). This implies changes in the definition of density and heat capacity at constantpressure close to the phase change interface. Far from the phase change interface, thedensity and heat capacity are unchanged.

98 |CHAPTER 1: RELEASE NOTESBackward Compatibility with Version 4.3b
INTERIOR FLUXES UPDATED

Because the interior flux variable definitions have been revised, models that use interior
fluxes in definitions, physics interfaces, or postprocessing show different results inversions 5.0 and later than in earlier versions.
IMPROVED ENERGY BALANCE

Changes introduced in the equation formulation to enable better energy balance mayslightly modify the results.
Among the changes, the reference enthalpy, HRef, the value of which is defined up toa constant, is now set to 0 J/kg at the reference temperature and pressure. Thischanges the absolute values of the enthalpy and several variables based on it. In
particular, the value of the convective heat flux is changed. Even the sign may bechanged in some cases. However, the quantity of interest, the net convective heat flux,
is identical because the shift induced by the change of HRef applies for the enthalpy
definition at the inlet as well as at the outlet.

Backward Compatibility with Version 4.3a
HEAT TRANSFER IN POROUS MEDIA

Old models using the Porous feature will be supported in the COMSOL Multiphysics
interface. However, it is recommended to replace this feature with Heat Transfer in
Porous Media (see Obsolete Features). For a model using the API, it will benecessary to update the model to use Heat Transfer in Porous Media.
SURFACE-TO-SURFACE RADIATIONThe surface radiosity, previously named J, is now named ht.J by default (assumingthat ht is the physics interface tag).
Models created using versions 4.3 and 4.3a that contain surface-to-surface radiation
support the old syntax in multiphysics interfaces. It is, however, recommended thatyou update the models to use the new syntax. Models created in a version before 4.2aneed to be opened in version 4.3 or 4.3a and resaved before being opened in 5.0 or alater version.
For a model using the API, you must update the model to use the new syntax.

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99

RADIATION IN PARTICIPATING MEDIAThe radiative intensity variable names, previously named I1 and so on, became ht.I1(when there are fewer than 10 discrete directions) or ht.I01 (when there are 10 ormore discrete directions) by default.
Models created in versions 4.3 and 4.3a that include radiation in participating media
support the old syntax in multiphysics interfaces. It is, however, recommended thatyou update the models to use the new syntax. Models created in a version before 4.2aneed to be opened in version 4.3 or 4.3a and resaved before being reopened in 5.0 ora later version. In addition, for all versions, it may be necessary to regenerate thedefault solver to get the correct solver settings.
The S2 quadrature in 2D has been replaced by the LSE symmetric quadrature. It has
been updated so that it coincides with the other quadratures. LSE symmetricquadratures were already used for S4, S6, and S8 in 2D and for all 3D quadratures.
This quadrature update can result in significant changes in 2D models using the S2
quadrature. However, the theoretical error is not different and the 2D and 3D
implementations are now consistent.

Backward Compatibility with Version 4.3
THE DEFAULT MODEL LIST HAS BEEN REMOVEDHeat transfer physics interfaces no longer have the default model list. This list was used
to change the default feature for heat transfer models. You can obtain a similar result
by adding the corresponding domain feature immediately below the default featureand setting its domain selection to All domains.
Any model files for Java® that modify the default model value require a manual update.
IMPROVED STABILIZATION OF HEAT TRANSFER IN SOLIDS

The streamline diffusion stabilization for Heat Transfer in Solids and Biological Tissue
features has been improved. It now accounts for contributions from linear source
terms from the Heat Source, Out-of-Plane Convective Cooling, Out-of-Plane Radiation, andOut-of-Plane Heat Flux features. This improves the robustness of the convergence whenthese contributions are large. This change may modify the convergence behavior ofexisting models.
FRAME SELECTION IN DISCRETIZATION SECTION

The Frame type list, which was previously available when a moving mesh was detected,
has been removed. The frame type is now controlled by the features.

100 |CHAPTER 1: RELEASE NOTESUPDATE OF FEATURE VARIABLE NAMES

In order to avoid name conflicts between feature variable names, some of them havebeen renamed. This change concerns contributive features. Because they arecontributing, it is possible to have similar features active on the same boundary. To
make it possible to distinguish the variables from each feature, the feature scope has
been introduced in the variable name so that variable names now use a prefix. Thesechanges affect the following feature variables:• Heat flux
• Out-of-plane heat flux
• Convective cooling• Out-of-plane convective cooling• Boundary heat source• Heat source• Line heat source• Point heat source• Edge heat flux/Point heat flux
• Electrochemical reaction heat flux
• Reaction heat flux
For example, in a Boundary Heat Source feature, ht.surf has been renamed into
ht.bhs1.surf (assuming that ht is the physics interface tag). In the Heat Flux
feature, the variable that was previously named ht.q0_hf1 is now ht.hf1.q0.
Any model files for Java® that use the old variable names in expressions (such as
expressions used for plotting or data evaluation that include such old variable names)
need to be updated manually.
NEW DEFAULT FLUID FEATURES AND OPAQUE SUBFEATURE

All MPH files created in version 4.3 are converted to appear and behave the same way
as in 5.0 or a later version.
Due to these new default features, model files for Java can be simplified. In addition,model files for Java that add the Fluid feature or the Opaque subfeature with the default
tag require a manual update to avoid duplicate tag conflicts.

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101

WEAK CONSTRAINTS UPDATE FOR FLUID FLOW USER INTERFACES

The weak constraint formulations for some boundary conditions in the followinginterfaces have been updated:• Laminar Flow
• Turbulent Flow, k-ε• Turbulent Flow, Low Re k-ε• Nonisothermal Flow
• Conjugate Heat Transfer
See the CFD Module release notes for details.
Weak constraints for the Interior Wall feature are no longer available.
REVISION TO THE TURBULENCE MODELS

The formulations of some variables in the turbulence models have been revised inorder to improve accuracy. Simulations using a turbulence model can display adifferent convergence behavior in versions 5.0 and later compared to version 4.3, andthe numerical result can differ slightly between the versions.

Obsolete Features
The following features have been removed:• Inflow Heat Flux (replaced by Inflow and Boundary Heat Source)• Electromagnetic Heat Source and Electromagnetic Heat Source (replaced byElectromagnetic Heating)• Boundary Thermoelectric Effect (merged with Thermoelectric Effect)• Convective Heat Flux (replaced by Heat Flux with Convective heat flux option)• Out-of-plane Convective Heat Flux (replaced by Out-of-plane Heat Flux with Convective
heat flux option)• Porous Matrix (replaced by Porous Medium)• Infinite Element (replaced by Infinite Element Domain declared in the Definitions node)• Electrochemical Heat Flux (replaced by Boundary Heat Source)• Reaction Heat Flux (replaced by Boundary Heat Source)• Heat Transfer in Participating Media (replaced by Heat Transfer with Radiation in
Participating Media)

102 |CHAPTER 1: RELEASE NOTESM E M S M o dule
New Functionality in Version 5.4
NEW PHYSICS INTERFACE: ELECTROMECHANICS, BOUNDARY ELEMENTS

The Electromechanics, Boundary Elements interface solves the same class of problems as
the Electromechanics interface, except it uses a boundary element discretization for theelectrostatics part of the model. Model setup can be easier, as infinite element domains
and moving mesh are not necessary.
CHANGES IN SYMMETRY AND ANTISYMMETRY FOR SOLID MECHANICS
IN 2D AXISYMMETRY

In the 2D axisymmetric version of the Solid Mechanics interface, the nodes Symmetry
and Antisymmetry are now obsolete. They have been replaced by the Symmetry Plane
node. The reason is that the only possible true symmetry in an axisymmetric model iswith respect to a cut perpendicular to the Z-axis. The old features allowed unphysicalconstraints.
NEW MODAL SUPERPOSITION STUDY TYPES

Two new predefined study sequences for modal superposition have been added: Time
Dependent, Prestressed, Modal and Frequency Domain, Prestressed, Modal. In both cases,
three study steps are generated, where the first one is a stationary step in which theprestress state used for the subsequent eigenfrequency computation is determined.
RENAMED STUDY TYPES

Some study types have been renamed in order to get a more consistent naming:• Frequency Domain Modal is now Frequency Domain, Modal• Time Dependent Modal is now Time Dependent, Modal• Prestressed Analysis, Eigenfrequency is now Eigenfrequency, Prestressed• Prestressed Analysis, Frequency Domain is now Frequency Domain, Prestressed
PARTICIPATION FACTORS FOR EIGENFREQUENCY STUDIESWhen you add an Eigenfrequency study from the Add Study window, a Participation
Factors node is now automatically added under Definitions, as long as there is at least
one structural mechanics physics interface in the model. You will thus always haveaccess to the participation factor variables after running such a study.

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103

MATERIAL ACTIVATION

It is now possible to activate a material in a stress free state using the new Activation
subnode under Linear Elastic Material in the Solid Mechanics and Membrane interfaces.
A user-defined logical expression is used for the activation. The same feature can also
be used to remove material. Typical applications are various types of manufacturing
processes where material is added.
HOMOGENIZATION OF PERIODIC MATERIALS

Inhomogeneous materials can often be represented by a unit cell that is assumed to bepart of a periodic structure. This is sometimes called a representative volume element(RVE). The new Cell Periodicity feature in the Solid Mechanics interface provides you
with several options for analyzing such unit cells:• Automatic computation of equivalent homogenized anisotropic material properties(stiffness, compliance, thermal expansion), which can be accessed as a Global
Material.
• Computation of the local stresses and strains in the unit cell, given external average
stress and strain fields.
• Computation of free thermal or hygroscopic expansion of the unit cell, given
average temperature or moisture concentration.
BURGERS VISCOELASTIC MODEL

One more built-in viscoelastic model has been added: the Burgers model. As with theother viscoelastic models, it is accessed by adding a Viscoelasticity subnode under the
Linear Elastic Material.
VOLUME REFERENCE TEMPERATURE

A new concept, volume reference temperature, has been introduced. It serves two
purposes: it replaces the earlier strain reference temperature for thermal expansion,and it is the temperature at which the mass density is computed. These two phenomena
are physically related to each other, and the default is to use the same value, defined asa Common model input. For the mass density, the concept is new and is used to avoid
violations of mass conservation. For thermal expansion, the default location where you
specify the strain free temperature has moved from the Thermal Expansion node or
Thermal Expansion multiphysics coupling to Common model input.
When you open an old model, the value of the strain reference temperature isconverted to a User defined volume reference temperature.

104 |CHAPTER 1: RELEASE NOTESUTILITY FUNCTIONS FOR EXTERNAL MATERIALSWhen programming your own constitutive relations using the external materials
functionality, there are several operations for which there is a recurring need. Examplesof this are various tensor operations, computation of principal values and orientations,and matrix inversion. There is now a library of utility functions that covers many
common operations employed when programming material models for solidmechanics.
TIME STEP PASSED TO EXTERNAL MATERIALSThe time or parameter step is now passed as an argument to the material function whenusing the General Stress-Deformation Relation socket.
NEW SETTINGS FOR MIXED FORMULATION

In earlier versions, a mixed (displacement-pressure) formulation could be activatedusing the Nearly incompressible material check box in a material model. It has been
replaced by the Use mixed formulation list with the following three choices: None,
Pressure formulation, and Strain formulation. The pressure formulation is the same
mixed formulation as before, while the strain formulation is new. Instead of a pressure,the volumetric strain is used as an extra degree of freedom.
CHANGES IN FLUID-STRUCTURE INTERACTION INTERFACESThe Fluid-Structure Interaction, Fixed Geometry multiphysics coupling present inprevious releases is now obsolete. It has been merged with an updated Fluid-StructureInteraction multiphysics coupling. This makes it easier to switch between the two
formulations. In the current version, the only difference lies in whether a Deforming
Domain is active on a fluid domain or not.
Old models where you have used Fluid-Structure Interaction, Fixed Geometry are notchanged. You are, however, advised to update to the new type of modeling.
RIGID DOMAIN IN 2D AXISYMMETRY

The Rigid Domain material model is now also available in 2D axisymmetry. It has onlya single degree of freedom: the axial translation.
RIGID CONNECTOR FOR EDGES AND POINTSThe selection in a Rigid Connector can now be a combination of boundaries, edges, andpoints. It is now also possible to add a rigid connector at the edge and point levels, aslong as there are no higher-order geometrical objects in the selection.

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FLEXIBLE FORMULATION OF RIGID CONNECTOR

There are now two formulations of the Rigid Connector feature, Rigid and Flexible. In
the default formulation, all the selected boundaries, edges, and points behave as if they
were connected by a common rigid body. In some cases, this gives an unwanted
stiffening or unrealistic local stresses. You can then switch to a flexible formulation
where the constraint is applied only in an average sense. The flexible formulation isavailable only for a rigid connector with a pure boundary selection and not when theselection also contains edges or points.
TABULAR OUTPUT OF EIGENFREQUENCIES

When running an Eigenfrequency study, a table containing the natural frequencies,
modal damping, and quality factors is now generated by default.
SPRING AND REACTION FORCES

A new reaction force variable containing the sum of reaction forces from constraints
and reaction forces from spring foundation has been added to all structural mechanics
physics interfaces. The variables, which are available in the result menus, are called
Total reaction force and have component names like solid.RFtotalx. If there arespring foundations in your model, you will find the forces under the category Springand Damping forces in the result menus.
REACTION-FREE SYMMETRY CONDITION

The symmetry conditions in the structural mechanics interfaces have been extended toaccount for cases where the symmetry plane is allowed to translate in the direction of
its normal rather than being a fixed plane. The main application is for use as a boundary
condition in truncated structures having no net reaction force. In the new section
Normal Direction Condition in the settings for the Symmetry node, you can adjust the
behavior of this boundary condition. There are four different options: No displacement(the default), Free displacement, Prescribed force, and Prescribed displacement.
ROLLER CONDITION WITH ANALYTICAL NORMAL ORIENTATION

The default roller constraint acts along a normal to the selected boundaries. The
normal is computed numerically. For a certain mesh node, this direction is kept
constant during the analysis, so it cannot represent finite sliding on a curved boundary.

106 |CHAPTER 1: RELEASE NOTESYou can now, however, prescribe that the boundary slides on an analytical surface.
There are two situations where you may need to do this:• The geometry or mesh representation of the actual boundary is imperfect. This canlead to unexpected locking of the deformation, since the computed normals do nothave the intended directions.
• In a geometrically nonlinear analysis, the use of an analytical surface makes it
possible to also model finite sliding along curved boundaries.
In the settings in the Roller node, select a Normal orientation, which can be either
Automatic, Plane, Cylinder, or Sphere.

New Models in Version 5.4
SQUEEZE-FILM DAMPING OF PERFORATED PLATESThis benchmark model compares the damping coefficients of perforated plates fromcomputation results versus experimental data. The simulation includes 18 different
geometric configurations. It uses the Bao’s perforation model, which is built into theThin Film Flow physics interface. Two limiting cases are also simulated: no perforationand zero relative pressure at the perforations.
S-PARAMETER OF A THIN-FILM BAW RESONATOR

This model shows how to compute the S-parameter for a piezoelectric MEMS device
by extending the tutorial Thin-Film BAW Composite Resonator. The measurement of
the S-parameter is commonly used to characterize such devices for RF applications.
The terminal feature in the Electrostatics physics interface provides straightforward
access to the computed S-parameters for frequency domain study types.
DISPERSION DIAGRAM OF A THIN-FILM BAW STRUCTURE

This model shows how to create dispersion diagrams from simulation results byextending the tutorial Thin-Film BAW Composite Resonator. The dispersion curve
can be plotted against both real and imaginary values of the wave number,corresponding to the propagating modes and evanescent modes, respectively. Eachmode can also be visualized by plotting its displacement field. The consideration aboutsuch propagating and evanescent modes is an important part of the process in selecting
appropriate design parameters for the layer structure of a BAW resonator.

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Backward Compatibility with Version 5.2
The friction slip velocity is no longer defined as a dependent variable. When runninga model using the COMSOL API, you will need to remove the reference to thisvariable in the solver settings. The friction slip velocity is usually defined as<comp>_<solid>_vslip_<pairname>, where <comp> is the tag of the component,<solid> is the tag of the Solid Mechanics physics interface where the Friction node isdefined, and <pairname> is the name of the contact pair.

Backward Compatibility with Version 4.3b
For models using contact, plot expressions are not updated when you open an oldmodel where the pair names have been edited manually. Also, opening an old model
where a pair name has been manually edited might affect the solver configuration. It
is recommended that you regenerate a new default solver configuration.

108 |CHAPTER 1: RELEASE NOTESMicrofluidics Module
New Functionality in Version 5.4
UPDATED PHYSICS INTERFACE: LAMINAR TWO-PHASE FLOW, MOVINGMESH

The Laminar Two-Phase Flow, Moving Mesh interface now uses the Deforming Domainfeature under Definitions. This facilitates model setup, as the fluid domain settings andboundary conditions are now specified in the Laminar Flow interface, and thedeforming domains and boundary conditions are set up under the Definitions node.
This also allows other physics to be included in a straightforward way, as the moving
mesh functionality is common to all physics in the model. It is now also possible tospecify a mass flux in the External Fluid Interface boundary condition.
UPDATED FLUX FORMULATION

Updated formulation for the Flux and No Flux nodes included in the Transport of
Diluted Species and the Transport of Diluted Species in Porous Media interfaces.
• The flux relative to the convective flux is prescribed instead of the total flux.
• The new formulation implies that the nodes can be used on a moving meshgeometry without compensating for the boundary velocity.
• Updated equation display for governing equations and boundary conditions.
Equations updated to be formulated in terms of the flux relative to the convective
flux.

Backward Compatibility with Version 5.3a
NO FLUX FORMULATION

The formulation of the No Flux feature has been changed in the Transport of Diluted
Species and Transport of Diluted Species in Porous Media interfaces in version 5.4 sothat the flux relative to the convective flux is set to zero. The new formulation is used
when opening a model from a previous session. In the previous formulation, the total
flux was set to zero.

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Backward Compatibility with Version 4.3a
The Free Molecular Flow and Transitional Flow user interfaces now form the
Molecular Flow Module. A Molecular Flow Module license is required to use theseinterfaces.

Backward Compatibility with Version 4.3
BRINKMAN EQUATIONS AND FREE AND POROUS MEDIA FLOW

The momentum equations in the Brinkman Equations interface and the Free andPorous Media Flow interface have been corrected. The term −Qbr·u/εp2 on the righthand side previously lacked the factor 1/εp2, where εp is the porosity.
MOBILITY

In physics interfaces modeling migration (for example, Transport of Diluted Species),
anisotropic mobility is now supported, and the mobility can be set to follow the
Nernst-Einstein relation. The default setting when making new models has beenchanged to the Nernst-Einstein relation. Model files for Java® generated prior to 4.3b
using migration will have to be modified manually to account for these changes.

110 |CHAPTER 1: RELEASE NOTESM i xe r M o dule
New Functionality in Version 5.4• All Mixer Module interfaces now use the Moving Mesh functionality under the
Definitions node in the Model Builder.
• The v2-f and Realizable k-ε turbulence models are now available in the Rotating
Machinery, Nonisothermal Flow interface.
• New studies for the Rotating Machinery, Nonisothermal Flow interfaces: Frozen
Rotor, One-Way Coupled, NITF; Frozen Rotor, One-Way Coupled with
Initialization, NITF; Time Dependent, One-Way Coupled, NITF; and Time
Dependent, One-Way Coupled with Initialization, NITF.
• All turbulence models are now available in the Rotating Machinery, Multiphase
Flow interface.
• Free Surface and Rotating Shaft boundary conditions are now available in the
Rotating Machinery, Multiphase Flow interface.
• A new Navier slip option is available for Interior Wall features in all Laminar Flowinterfaces.
• The default solver for the fluid flow interfaces now has the Reuse sparsity patterncheck box enabled in the Advanced solver node’s Assembly Settings section. Thissetting typically reduces computation time by around 10% for time-dependent
models.

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Molecular Flow Module
Backward Compatibility with Version 5.0 and Earlier
Due to the fact that multiple species are now supported, some variable names havechanged. In general, variables will now have _G appended to their names, where G is
the name specified for the Incident molecular fluxes in the Dependent Variables section.
So, if a model is updated and resolved, the expressions used in results should bechanged as follows:• The number density should be changed from fmf.N to fmf.N_G.
• The pressure should be changed from p to fmf.p_G.
• The reconstructed number density should be changed from fmf.N to
fmf.ndr1.Nr_G, where ndr1 is the tag of the Number Density Reconstruction
feature.
• Any other variables can be updated using the Replace Expression button available
during results processing.
In addition, new variables exist for the total pressure, number density, and so on:• The total number density, fmf.ntot.
• The total pressure, fmf.ptot.
• The total incident molecular flow, fmf.Gtot.

112 |CHAPTER 1: RELEASE NOTESMultibody Dynamics Module
New Functionality in Version 5.4
FLEXIBLE ATTACHMENT

There are now two formulations of the Attachment feature: Rigid and Flexible. In thedefault formulation, all the selected boundaries behave as if they were connected by acommon rigid body. In some cases, this behavior results in an unwanted stiffening or
unrealistic local stresses. To avoid that, you can then switch to a flexible formulation
where the constraint is applied only in an average sense.
FLUID-STRUCTURE INTERACTION

Two predefined multiphysics interfaces for coupling the Multibody Dynamics
interface with fluid flow have been added: Fluid-Multibody Interaction and FluidMultibody Interaction, Assembly. The former uses a standard Fluid-Structure Interaction
multiphysics coupling, and it is used when the geometry is in the Union state.
For multibody dynamics models, it is, however, more common that the Assembly stateis used when building the geometry. In this case, the Fluid-Multibody Interaction,
Assembly interface must be used. When invoked, it generates the new Fluid-StructureInteraction, Pair multiphysics coupling.
ROLLING ELEMENT BEARING

Models for six types of rolling element bearings have been added to the Multibody
Dynamics interface:• Deep groove ball bearing• Angular contact ball bearing• Self-aligning ball bearing• Spherical roller bearing• Cylindrical roller bearing• Tapered roller bearing
Each of the bearings can have either a single or double row of rolling elements.
The bearing model includes a nonlinear representation of the contact stiffness between
the rolling elements and the inner and outer races. To include such a bearing in yourmodel, add the Radial Roller Bearing node, which requires the Rotordynamics Module.

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LOCAL FRAME FOR RESULT PRESENTATION

You can now evaluate and plot displacements relative to any rigid domain, attachment,
or gear. In the Results section of the Multibody Dynamics interface settings, select any
such object from the Body defining reference frame list. You will then get access tovariables for the displacements and velocities relative to that object.
ROLLER CONDITION WITH ANALYTICAL NORMAL ORIENTATION

The default roller constraint acts along a normal to the selected boundaries. The
normal is computed numerically. For a certain mesh node, this direction is kept
constant during the analysis, so it cannot represent finite sliding on a curved boundary.
You can now, however, prescribe that the boundary slides on an analytical surface.
There are two situations where you may need to do this:• The geometry or mesh representation of the actual boundary is imperfect. This canlead to unexpected locking of the deformation, since the computed normals do nothave the intended directions.
• In a geometrically nonlinear analysis, the use of an analytical surface makes it
possible to also model finite sliding along curved boundaries.
In the settings in the Roller node, select a Normal orientation, which can be either
Automatic, Plane, Cylinder, or Sphere.

114 |CHAPTER 1: RELEASE NOTES

Nonlinear Structural Materials
ModuleNew Functionality in Version 5.4
MULLINS EFFECTThe Mullins effect is a damage-like phenomenon in rubber, where the stress-strain
curve depends on maximum stress that the material has been subjected to. You can
now model this effect by adding a Mullins Effect subnode under a Hyperelastic Material.
There are two different models available for the Mullins effect: Ogden-Roxburgh andMiehe.
DAMAGE MODELINGFor brittle materials, damage caused by cracking is an important failure mechanism.
The new Damage subnode under Linear Elastic Material makes it possible to incorporate
continuum-based damage models, where the material softens as an effect of theseverity of the loading. Various effective scalar damage models based on equivalentstrain measures (Rankine, Smooth Rankine, Norm of elastic strain tensor, and User
defined) are available. You can also select different rules for the damage evolution:
Linear strain softening, Exponential strain softening, and User defined.
Softening material models are numerically problematic due to strong localization of
the damage. For this reason, you often need to use regularization methods thatsmooth the damage over a finite region. Two such methods are available: Crack band
and Implicit gradient.
The damage functionality is available with both the Nonlinear Structural Materials
Module and the Geomechanics Module. With the latter, there are also models specificto concrete available.
TRANSFORMATION DIRECTION CONTROL FOR SHAPE MEMORY ALLOYS

You can now prescribe the transformation direction for the Lagoudas model in the
Shape Memory Alloy material. Use the new Transformation direction setting. This setting
can significantly improve convergence for the common cases when the transformation
direction is known a priori.

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CHANGES FOR HYPERELASTIC MATERIALS WITH LOW COMPRESSIBILITY

Many hyperelastic materials, like rubber, have very low compressibility. To solve suchproblems, special numerical methods, like mixed formulations, must be used. The
treatment of incompressibility or near incompressibility has been changed for most
hyperelastic materials. A Compressibility list has been added. From that, you can choose
one of the following material types:• Compressible material. This option is only available for those material models that are
intended to incorporate a significant flexibility.
• Nearly incompressible material, quadratic volumetric strain energy. This is the type of
mixed formulation that was available in previous versions, when the now obsolete
Nearly incompressible material check box was selected.
• Nearly incompressible material, Hartmann-Neff volumetric strain energy. This new
method is similar to the previous formulation but is more accurate in maintaining
incompressibility.
• Incompressible material. In this new formulation, a constraint is used in order toenforce incompressibility.
MULTIPLICATIVE DECOMPOSITION IN NONLINEAR ELASTIC MATERIAL

Even though the Nonlinear Elastic Material is mainly intended for small strains, it canalso be used under geometric nonlinearity. The removal of inelastic strains from thetotal strains is now done using multiplicative decomposition, just as for other materials.
By using the Additive strain decomposition check box, you can retrieve the formulation
previously used.
BURGERS VISCOELASTIC MODEL

One more built-in viscoelastic model has been added: the Burgers model. As with theother viscoelastic models, it is accessed by adding a Viscoelasticity subnode under the
Nonlinear Elastic Material node.

New Models in Version 5.4
SHAPE MEMORY ALLOY SELF-EXPANDING STENTThis model studies the crimping at low temperature of a shape memory alloy stent,
followed by heating up to body temperature. The results show the stress increaseduring heating and the pressure applied to the inner wall of the artery.

116 |CHAPTER 1: RELEASE NOTESBRITTLE DAMAGE IN UNIAXIAL TENSIONIn this tutorial model, different methods for modeling brittle damage are compared ina uniaxially loaded bar. The new Damage feature is used. The localization of thedeformation during fracture is studied using different discretization orders andregularization methods.
CRACKING OF A NOTCHED BEAM

In this example, two models for brittle damage are used to evaluate the fracture of anotched concrete beam subjected to three-point bending. The new Damage feature isused. The results are compared with experimental data.

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Optimization Module
New Functionality in Version 5.4
TOPOLOGY OPTIMIZATION USING HELMHOLTZ FILTERINGThe capability for topology optimization has been improved with support forHelmholtz filtering, projection, and interpolation. A new Density Model feature
available under Definitions>Topology Optimization in model components provides
settings for adding filtering, projection, and interpolation.
PARAMETRIC SWEEPS AND DERIVATIVE-FREE OPTIMIZATION

It is now possible to add a Parametric Sweep study step over an Optimization study stepand vice versa if the Optimization study uses a derivative-free method (Nelder-Mead,
Monte Carlo, BOBYQA, COBYLA, or Coordinate search). There can only be one
Optimization study step, while more Parametric Sweep study steps are allowed.
OTHER IMPROVEMENTS• The Keep objective values in table check box is now available for LevenbergMarquardt and MMA optimization methods with least-squares objectives. It isenabled by default. This means that an objective table will be made while running.
Consequently, the API backward compatibility can be lost in some cases. API users
need to update the code that tries to access or make some specific table after the
optimization has been run. The table could have already been used by the
optimization solver.
When the data source is Results table or Local table, you can also select items in the
Data column by clearing or selecting the corresponding check box in the Use column.

You can then, for example, use the same results table to contain both experimental
input and output data when performing a time-dependent optimization using atime-dependent load.
• Equation display has been added to the Optimization interface.
• Improved stability on Windows® 10.

118 |CHAPTER 1: RELEASE NOTESNew and Updated Models in Version 5.4
A new model, Exporting and Importing a Topology Optimized Hook
(hook_optimization_stl), is available and includes a study of the optimal material
distribution in a hook.
In addition, the following models have been updated to make use of the enhanced
capabilities for topology optimization: mbb_beam_optimization, loaded_knee,
tesla_microvalve_optimization, and reversed_flow. In earlier versions, thesemodels used a Tikhonov regularization. They now make use of a filter where the meshedge length generally works as a default for the filter length, which makes it possible
to eliminate a parameter in the models — a parameter that otherwise required
substantial trial and error to get right.

Backward Compatibility with Version 4.3a
The Optimization check box in the Stationary and Time Dependent study steps havebeen removed. Instead, use the Optimization study step. The Optimization check box
does appear in models created in earlier versions of COMSOL Multiphysics where you
have selected that check box.

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Particle Tracing Module
New Functionality in Version 5.4
ACCUMULATORS FOR VELOCITY REINITIALIZATIONThe Accumulator is now available as a subnode of the Velocity Reinitialization node.
When a particle is redirected or stopped by the Velocity Reinitialization, theaccumulated variables can be incremented in the mesh element occupied by theparticle at that instant.
OFFSET VELOCITY DISTRIBUTIONS OF RELEASED PARTICLESWhen particles are released with a velocity distribution, it is possible to offset all initial
velocities in the distribution by an arbitrary expression. In previous versions, it was only
possible to offset the velocity distribution by the velocity of a rotating frame ofreference with the Rotating Frame feature.
The main use for this functionality is to trace particles in a frame of reference that ismoving at some velocity relative to the laboratory frame.

New Applications in Version 5.4
QUASI-2D TURBOMOLECULAR PUMPThe Monte Carlo simulation of flow in a turbomolecular pump can be greatly
simplified if the mean radius of the blades is much greater than the spacing between
them. Under these conditions, the rotating blades of the pump can be approximatedas an infinite row of blades having only translational velocity.
This benchmark model shows the effect of blade velocity, angle, and spacing on thetransmission probability of molecules across a single-stage turbomolecular pump in thefree molecular flow regime. The results agree well with earlier publications using thesame simplifying assumptions.

Backward Compatibility with Version 5.3 and Earlier
NOMENCLATURE CHANGES FOR MULTIPLE PARTICLE SPECIESThe Override Properties feature has been renamed to Particle Properties to emphasizethat it can be used to release multiple species of particles in the same model. The list

120 |CHAPTER 1: RELEASE NOTESInherit Properties in the settings for most particle release features, such as Inlet andRelease from Grid, has been renamed to Released particle properties.
TURBULENT DISPERSION CHANGESThe turbulent dispersion models used by the Drag Force in the Particle Tracing for
Fluid Flow interface have been modified and a deprecated turbulent dispersion model
has been removed.
The option Discrete random walk, variable time step has been removed from the
Turbulent dispersion model list. When an old model using this obsolete option is loadedin version 5.3a, the Discrete random walk option is now selected. However, Discreterandom walk actually behaves more like the old Discrete random walk, variable time stepmodel because it only samples the turbulent velocity perturbation at discrete timeintervals based on the eddy lifetime or eddy crossing time in the flow.
CHANGES TO RELEASE FROM EDGE AND POINT

In the Particle Tracing for Fluid Flow interface, the Release from Edge and Release from
Point features now allow the initial particle velocity to be selected from a list containing
previously computed velocity fields, similar to the behavior of the Release and Inletfeatures. This makes the Release from Edge and Release from Point features easier tocouple with another physics interface that models the fluid flow.
CHANGES TO PERIODIC ELECTRIC AND MAGNETIC FORCES

In models built in version 5.3 or earlier, if an Electric Force or Magnetic Force waspresent and the Multiply force by phase angle check box was selected, then in version
5.3a, Time harmonic will be selected from the new Time dependence of field list, which
replaces this check box.

Backward Compatibility with Version 5.2a and Earlier
REFERENCE EDGE FEATURES HAVE BEEN REMOVED

The Reference Edge subnode, which was previously used to specify the orientation of
the transverse beam directions for the Particle Beam feature in 3D, has been removed.
Instead, the orientation of the transverse beam directions is specified using an extra
selection field in the settings window for the Particle Beam feature itself. Similarly, theReference Point subnode for specifying the beam center has been replaced by an extra
selection in the settings window for the Particle Beam feature.

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Backward Compatibility with Version 5.2
TURBULENT DISPERSION CHANGESIn the settings window for the Drag Force for the Particle Tracing for Fluid Flowinterface, the Turbulent dispersion check box has been replaced by the Turbulent
dispersion model list. If the check box is selected in a model created in version 5.2 orearlier, then after opening the model in version 5.2a, the option Discrete random walk
will be selected from the list. If the check box is cleared, then None will be selected fromthe list.
PARTICLE DENSITY SPECIFICATIONS MERGED

In version 5.2, when specifying particle properties using the Particle Properties node orOverride Properties node in the Particle Tracing for Fluid Flow interface, it is possible
to specify two different values of the particle density, depending on whether theCompute particle mass check box is selected. In version 5.2a, these two values have been
merged into a single parameter value; that is, the value or expression for the Particle
density will be retained when selecting or clearing the Compute particle mass check box
in the physics interface Advanced Settings section.
PARTICLE BEAM CHANGESThe names of several settings have been changed in the Particle Beam feature for theCharged Particle Tracing interface.
In the Sampling from phase space distribution list, Uniform has been renamed KV.
In the Longitudinal velocity distribution list, Uniform has been renamed None andGaussian has been renamed Normal.
The parameters Position refinement factor and Release distribution accuracy order havebeen removed. Due to some changes in the algorithm for initializing particle positions,in version 5.2a, the distribution of particle positions no longer depends on the finite
element mesh and may differ from the distribution in version 5.2.

Backward Compatibility with Version 5.1
RENAMED PHYSICS INTERFACE SETTINGSThe Release type list in the settings windows for the Charged Particle Tracing andParticle Tracing for Fluid Flow interfaces in earlier versions has been renamed Particle
release specification. For the Charged Particle Tracing interface, the options Static and

122 |CHAPTER 1: RELEASE NOTESTransient have been renamed to Specify current and Specify release times (the default),

respectively. For the Particle Tracing for Fluid Flow interface, the options Static andTransient have been renamed to Specify mass flow rate and Specify release times (thedefault), respectively.

Backward Compatibility with Version 5.0 and Earlier
OLD NODES FOR PARTICLE-FIELD AND FLUID-PARTICLE INTERACTIONSARE OBSOLETE

The old Particle-Field Interaction and Fluid-Particle Interaction nodes, which could be
added directly to the Charged Particle Tracing and Particle Tracing for Fluid Flowinterfaces, respectively, are now obsolete. They will be removed in a future version.
Simulations of particle-field and fluid-particle interactions should instead use thededicated multiphysics nodes.
ELASTIC COLLISION FORCE NODE HAS BEEN REPLACED

If a model created in version 5.0 or earlier containing the Elastic Collision Force node is
opened in version 5.1 or later, this node will be replaced. If the Collision model in theold Elastic Collision Force node was set to Monte Carlo, a Collisions node with the Elastic
subnode will be created. If instead the Collision model was set to Friction, the Friction
Force subnode will be added.

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Pipe Flow Module
NEW MULTIPHYSICS COUPLINGS BETWEEN THE PIPE FLOW INTERFACEAND SINGLE-PHASE FLOW INTERFACES

Connecting a pipe segment modeled with the Pipe Flow interface with a 3D singlephase flow body is significantly easier through the introduction of the newmultiphysics coupling: Pipe Connection. The old Pipe Connection nodes inside the Pipe
Flow interface and Laminar Flow Interface are now obsolete, since the samefunctionality is available in a more convenient manner using this new multiphysics
coupling.

Backward Compatibility with Version 5.1 and older
REVISED FORMULATION OF THE PIPE FLOW INTERFACE

The Pipe Flow interface has been amended in version 5.2 with an inertial term. The
stabilization and element shape functions have also been changed. Models created inprevious versions will be opened using the old interface with a notification. For newmodels, only the new interface is available in the physics interface list.

124 |CHAPTER 1: RELEASE NOTES

Plasma Module
New Functionality in Version 5.4
MODIFIED PHYSICS INTERFACE: BOLTZMANN EQUATION, TWO TERMAPPROXIMATIONThe Boltzmann Equation, Two-term Approximation interface has been redesigned and is
now available in 0D instead of 1D.
GLOBAL MODELING OF NON-MAXWELLIAN DISCHARGES

It is now possible to compute the EEDF using a two-term approximation of the
Boltzmann equation for global plasma models.
OTHER NEW FEATURES

Some other key new features include:• The transport properties for electrons can now be computed from the EEDF
directly.
• A pulsed option has been added to the Metal Contact feature in the Plasma, Time
Periodic interface. This allows the discharge to be driven by a pulse rather than acontinuous application of the power.
• A Species Group feature has been added to the Plasma, Time Periodic interface, which
can be used to improve mass conservation in models where there is a chemicalcomposition of multiple different elements (for example, a mixture of Ar/N2).
• A Species Constraint Group feature has been added to the Plasma and Plasma, Time
Periodic interfaces that can be used to constrain the mole fraction of a given species.
This is useful for complex chemistries, as you no longer have to deactivate andreactivate species and reactions during model development.
• The default solver settings for the Plasma, Time Periodic interface have been
improved. The new settings may decrease the number of iterations required forconvergence and are more robust.

New and Updated Applications and Models in Version 5.4
NEW MODELS• Pulsed CCP Discharge.

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• Global Model of an Argon Discharge with non-Maxwellian EEDF.

Backward Compatibility with Version 5.3a and Earlier
Due to the way the detailed balance is computed for excitation collisions, models set
up from scratch could provide different results from the same model in version 5.3a.
Models are most likely to be affected if:• The mole fraction of the metastable species is high.
• The electron density is very high (above around 1E20 1/m3).
The new method for computing the detailed balance is more accurate and physicallycorrect than the method used in version 5.3a and previous.

Backward Compatibility with Version 5.3 and Earlier
There have been several changes that could affect the solution obtained when runninga model in version 5.3a versus 5.3 or earlier. This is due to the following changes andbug fixes:• When electron impact reaction rate constants are computed from cross section data,
due to a bug, the result will be different for the Maxwellian or Druyvesteyn electronenergy distribution functions. For DC discharges, where Townsend coefficients arerecommended, this should not make much of a difference. For inductively coupledor microwave discharges, the average electron density and plasma potential couldchange by as much as 5%, but typically around 2%. If significant differences in thesolution are obtained, it is recommended that you contact support@comsol.com.
• Surface species are no longer available from the context menu. Instead, surface
species will appear in the Model Builder when a surface reaction containing surface
species is added. If the surface reaction is deleted, then the dependent surface species
will also be deleted.
• The rate constant for a surface reaction that uses sticking coefficients has changed,
and is now proportional to the molecular weight of the reactant instead of the mean
molecular weight. In systems where the molecular weight is the same for all species,
this change won’t affect the results. In models containing species with very different
molecular weights, the surface reaction rates may change according to the squareroot of the molecular weight of the reactant divided by the mean molecular weight.
In such systems, it is recommended to activate the new Mixture diffusion correction
property, which adds additional correction terms to the mass flux vector for the126 |CHAPTER 1: RELEASE NOTES

heavy species. Overall discharge properties should not be significantly affected bythis change.
• The definition of surface site concentrations and surface reaction rate rates has beencorrected for models that include a surface chemical mechanism where the surface
species have different site occupancy numbers. This should only result in smallchanges to the solution, if any. The total surface site concentration is now a propertyon the physics interface level, rather than computed for each species on the featurelevel.
• The equation to compute binary diffusion coefficients from characteristic lengthparameters has changed. This may produce very slight changes in the diffusion
coefficients for the heavy species in the Plasma and Heavy Species Transportinterfaces. Any change in the solution due to this should be a tiny fraction of apercent.

Backward Compatibility with Version 5.2 and Earlier
The old Inductively Coupled Plasma and Microwave Plasma interfaces can still be
opened, edited, and solved. When such a model is opened, a warning is given
indicating that the interface is obsolete and will eventually be removed.

Backward Compatibility with Version 5.1
Models using the Reduced Electric Fields study will interpret the unit in the edit field
for the Reduced electric fields as Townsend. For example, when opening a model
created in version 5.1, if the value for the Reduced electric fields was 10, this will now
appear as 10[Td] in the study settings.

Backward Compatibility with Version 4.4
Old models will be updated to use the new boundary conditions, but re-solving amodel still gives the same results as before. The following changes to the model are
made upon opening:• If an Electric Potential feature is applied to boundaries adjacent to a Plasma Modelfeature, it is converted to a Metal Contact feature. The settings from the originalmodel are retained. If an Electric Potential feature is applied to boundaries adjacent
to a Charge Conservation feature, it remains the same.
• If an Electric Potential feature is applied to a combination of boundaries adjacent to
a Plasma Model and Charge Conservation feature, a Metal Contact feature is created for

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the boundaries adjacent to the Plasma Model feature, and the Electric Potential
feature remains on boundaries adjacent to the Charge Conservation feature.
• Any External Surface Charge Accumulation boundary conditions are replaced by a newDielectric Contact feature. The settings from the original model are retained. The
External Surface Charge Accumulation boundary condition is now obsolete.

128 |CHAPTER 1: RELEASE NOTESRay Optics Module
New Functionality in Version 5.4
ENHANCEMENTS TO THE PART LIBRARY

The Part Library for the Ray Optics Module has been overhauled in Version 5.4, withseveral major benefits.
Because the lenses and mirrors have been substantially changed, legacy parts with theold geometry sequences will be available for a limited time.

Fewer Internal Boundaries
The lenses in the new Part Library generally have fewer internal edges compared totheir counterparts in version 5.3a. The mesh discretization error for reflection andrefraction is usually the worst for rays that reach a boundary element adjacent to anedge in 3D, therefore the newer parts are much less prone to discretization error. The
result is significantly better accuracy when tracing rays through complicated opticalsystems in version 5.4.
NEW PARTS AND PART VARIANTS

The Conic Mirror Off Axis 3D part is now available as either a standard or standalone
variant. This affects the shape and orientation of the face opposite the reflecting
surface.
The lens parts Spherical Equi-Concave, Equi-Convex, Plano-Concave, and PlanoConvex lenses can each be specified using one of four variants:• Radius of curvature and center thickness• Effective focal length and center thickness• Radius of curvature and edge thickness• Effective focal length and edge thickness
The following new parts are also available:• Elliptical Planar Mirror• Spherical Mirror• Rectangular Planar Annulus

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OPTICAL DISPERSION MODELSThe Medium Properties node for the Geometrical Optics interface now supports a wide
range of popular optical dispersion models, such as the Sellmeier equation and its
variants. If an optical material having a certain set of optical dispersion coefficients isloaded into the Geometrical Optics model, then the dispersion relation can be detected
automatically. This makes it possible to trace rays through glasses made by different
manufacturers, which might use different sets of optical dispersion coefficients.
Some of the built-in optical dispersion models include temperature dependence,
making it easier to set up and run high-fidelity structural-thermal-optical-performance(STOP) analyses.
WAVELENGTH DISTRIBUTIONS AT RAY RELEASESPolychromatic light can now be specified in one of two ways: either specifying a
distribution of frequency values or a distribution of vacuum wavelengths.
IMPROVED ACCURACY FOR RAY TRACING IN ABSORBING MEDIAThe algorithm for computing ray intensity power in an absorbing medium, where therefractive index is complex-valued, has been improved. The new algorithm hassignificantly less numerical error, especially when the time steps or optical path lengthintervals in the study are very large.
GEOMETRY NORMALS FOR RAY-BOUNDARY INTERACTIONSThe Use geometry normals for ray-boundary interactions check box can be selected in
the settings for the Geometrical Optics interface. If the geometry is undeformed, thiscauses the rays to query normal directions from the parameterized geometry rather
than the boundary mesh, if the normals can be accessed in this way. Selecting this checkbox makes it possible to trace rays in an undeformed configuration more accurately,even if the mesh is not very fine.
NEW OPTION FOR INTENSITY COMPUTATION: COMPUTE POWER

It is now possible to solve for just intensity, just power, or both, along the ray paths.
With either intensity or power, the polarization along each ray is known.
The algorithm for reinitializing ray intensity and power is now significantly morerobust for any intensity computation method. In particular, models of enclosed
systems, where the wavefront is not well-defined and rays can undergo a large numberof reflections or refractions, are much more robust and accurate in version 5.4
compared to version 5.3a.

130 |CHAPTER 1: RELEASE NOTESNew Applications in Version 5.4
NEWTONIAN TELESCOPE

This tutorial model shows how to trace unpolarized light rays through a Newtonian
telescope. The incoming light is reflected off a paraboloidal mirror onto a flat,
elliptically shaped secondary mirror that folds the optical path by 90 degrees toward aflat focal plane. The telescope geometry is parameterized in terms of the primary
mirror’s focal length and diameter as well as the distance of the focal plane from theoptical axis.
HUBBLE SPACE TELESCOPE

The Hubble Space Telescope (HST) is an example of a standard Cassegrain telescope.
The “General Conic Mirror On Axis 3D” part from the COMSOL Multiphysics Part
Library is used to construct the HST Ritchey-Chretien geometry. Multiple releasefeatures are used to generate on- and off-axis ray and spot diagrams.
PETZVAL LENS STOP ANALYSIS, ISOTHERMALThis model demonstrates an integrated structural-thermal-optical performance(STOP) analysis of an optical system. The Petzval Lens tutorial is used as the basis forthis model, together with a simple barrel geometry. A Parametric Sweep is performed
over several uniform temperature values and the effect on the displacement fields andimage quality as a function of temperature is shown.
PETZVAL LENS STOP ANALYSISThis model demonstrates an integrated structural-thermal-optical performance(STOP) analysis of an optical system. The Petzval Lens tutorial is used as the basis forthis model, together with a simple barrel geometry. The lens assembly is placed insidea thermo-vacuum enclosure where the exterior temperature is significantly different
from the interior. The lens assembly is exposed to this exterior via a pair of windows.
The resulting temperature gradients and displacement fields within the optical system
are shown as well as the effect on image quality.

Backward Compatibility with Version 5.3 and Earlier
DIFFRACTION GRATING SETTINGS MOVED TO A SUBNODE

In version 5.3 and earlier, the Grating feature for the Geometrical Optics interface
automatically released transmitted and reflected rays of diffraction order zero. In

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version 5.3a, the rays of diffraction order zero are controlled by a Diffraction Ordersubnode, as are all other diffraction orders that might be released.
NEW OPTIONS FOR SPECIFYING DIFFRACTION GRATING ORIENTATIONIn the Grating feature for the Geometrical Optics interface, the options to control
grating orientation in 3D have been reorganized and expanded. It is now possible tospecify either the direction of the grating lines or the direction of periodicity in thegrating surface. The input Grating orientation specification has been renamed Directionof grating lines.
NEW OPTIONS FOR SPECIFYING REFLECTANCE OR TRANSMITTANCE

In the Geometrical Optics interface, the settings to control Thin dielectric films on
boundary in the settings for the Material Discontinuity feature have been renamed andrearranged.
The old options Single layer, specified reflectance and Single layer, specified
transmittance have been renamed to Specify reflectance and Specify transmittance,

respectively. For both of these options and for the Anti-reflective coating option, which
has not been renamed, the Treat as single layer dielectric film check box is selected when
opening the model in version 5.3a. Otherwise, this check box is cleared, which is thedefault behavior.
ADJUSTMENT TO THE RAY TERMINATION FEATURE

In the Ray Termination feature for the Geometrical Optics interface, the Termination
criteria list has been renamed Additional termination criteria.
REMOVED CHECK BOXES FOR OBSOLETE FUNCTIONALITY

In the settings for the Geometrical Optics interface, the Allow propagation outside
selected domains check box has been removed. This check box was flagged as obsolete

in version 5.3, so clearing it would have created a Warning node.
In the Settings window for the Release from Grid feature, the check box Suppress
interaction with coinciding exterior boundaries has also been removed.

Backward Compatibility with Version 5.2a and Earlier
REFERENCE EDGE FEATURES HAVE BEEN REMOVED

The Reference Edge subnode, which was previously used to specify the orientation ofsome optical components in 3D, has been removed. Instead, the orientation of these132 |CHAPTER 1: RELEASE NOTEScomponents is specified directly in the parent feature settings using an extra selection
input. The following features are affected:• Linear Polarizer• Linear Wave Retarder• Mueller Matrix• Grating

Backward Compatibility with Version 5.2
ANISOTROPIC REFRACTIVE INDICES CAN NO LONGER BE SPECIFIED

In version 5.2 and earlier, it is possible to specify an anisotropic refractive index in thesettings window for the Medium Properties node, despite the fact that the anisotropy of
the refractive index is not taken into account when modeling ray propagation. In
version 5.2a, only isotropic refractive indices can be specified in the settings window
for the Medium Properties node. If an anisotropic refractive index was specified in anolder version, then when opening the model in version 5.2a, all of the diagonal terms
will be populated using the first diagonal value and all off-diagonal terms will be set tozero.
RENAMED INTENSITY COMPUTATION METHODSThe options in the Intensity Computation list in the settings window for theGeometrical Optics interface have been renamed.
• Using principal curvatures has been renamed to Compute intensity.
• Using principal curvatures and ray power has been renamed to Compute intensity andpower.
• Using curvature tensor has been renamed to Compute intensity in graded media.
• Using curvature tensor and ray power has been renamed to Compute intensity andpower in graded media.
RENAMED POLARIZATION SETTING

In the Initial polarization type list, available for most ray release features in theGeometrical Optics interface, the option Partially coherent has been renamed toPartially polarized.

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CHANGES TO PERTURBATIONS FOR SOLAR RADIATION

The treatment of perturbations due to sunshape and surface roughness has beenchanged in version 5.2a. This change affects the Illuminated Surface and Solar Radiation
features for the Geometrical Optics interface.
The Use corrections for finite source diameter check box has been replaced by theCorrections for finite source diameter list. If the check box was selected, Create light
cones at release points will be selected from the list after opening the model in version
5.2a. If the check box was cleared, None will be selected from the list.
For the Illuminated Surface, the Standard deviation of the angle of incidence parameterhas been renamed Surface slope error and is now used to define a Rayleigh distribution
for perturbations to the surface normal, rather than the angle of incidence of radiation.
To account for the different effect that the surface slope error has on the model, any
value or expression entered for the Standard deviation of the angle of incidence in version
5.2 or earlier will be divided by 2, before being used to specify the Surface slope error
in version 5.2a.
The Number of rays in wave vector space Nw,r has been removed. The effect of surface
roughness can no longer multiply the number of degrees of freedom created by arelease feature at each release point.
ACTIVATION CONDITIONS ON OPTICAL COMPONENTS

The following boundary conditions require some form of ray intensity computation inorder to have any effect on the solution:• Linear Polarizer• Linear Wave Retarder• Circular Wave Retarder• Ideal Depolarizer• Mueller Matrix
If any of these features is present in a model created in version 5.2 or earlier, and Noneis selected from the Intensity computation list in the settings window for theGeometrical Optics interface, then the feature will be automatically disabled when themodel is opened in version 5.2a. To enable these features, select any option other thanNone from the Intensity Computation list.

134 |CHAPTER 1: RELEASE NOTESBackward Compatibility with Version 5.0
RENAMED SETTINGS

The Wall condition Bounce has been renamed to Specular reflection.
CHANGES TO FREQUENCY-DEPENDENT MATERIAL PROPERTIESThe Frequency-dependent refractive indices check box has been renamed to Allow
frequency distributions at release features.
Expressions involving the ray frequency must always be included within the noenv()
operator. Some expressions for user-defined refractive indices may fail to be evaluatedproperly in version 5.2a unless this operator is applied.
THIN DIELECTRIC FILM SETTINGS

In version 5.0, if the ray intensity is computed, the option to add Thin Dielectric Filmnodes to a Material Discontinuity node is always available. In version 5.2a, the Thin
Dielectric Film subnode can only be added if Add layers to surface or Add layers tosurface, repeating is selected from the Thin dielectric films on boundary list in the Material
Discontinuity settings window. If a model created in version 5.0 is opened in version
5.2a, and any Thin Dielectric Film nodes have been added, then Add layers to surface isselected from the Thin dielectric films on boundary list instead of the default None.
CHANGES TO THE CIRCULAR WAVE RETARDERThe Retardance of the Circular Wave Retarder now indicates the rotation angle of thepolarization ellipse of a ray that passes through the device. In version 5.0, theretardance corresponds to half of this rotation angle. The behavior of the Circular Wave
Retarder is now consistent with the documentation. If a model created in version 5.0
is opened in version 5.2a, the expression for the Retardance of any Circular Wave
Retarder node is multiplied by 2.
OBSOLETE DEPOSITED RAY POWER NODEThe Deposited Ray Power node for absorbing domains is obsolete and will be removed
in future versions. For simulations in which rays generate heat due to absorption, theRay Heat Source multiphysics node should be used instead.

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RF Module
New Functionality in Version 5.4
ADDITIONAL RF MATERIAL LIBRARY FOR SUBSTRATESThe RF Module enhances the RF material library with more than 40 substratematerials from Isola group to assist in modeling printed RF, microwave, andmillimeter-wave circuits.
UNIFORM ANTENNA ARRAY FACTOR FUNCTION

It is possible to evaluate the radiation pattern of an antenna array quickly from a single
antenna radiation pattern by using an asymptotic approach, such as multiplying the farfield of a single antenna with a uniform array factor.
3D FAR-FIELD AND RCS FUNCTIONS FROM 2D AXISYMMETRICCOMPONENT MODEL

2D axisymmetric modeling becomes more useful for a quick estimation of the far-field
response of the equivalent 3D model by utilizing new far-field functions. 3D far-fieldnorm functions in 2D axisymmetric geometry are available in these cases:• Antenna models using circular port excitation with a positive azimuthal mode
number• Scattered field analysis excited by the predefined circularly polarized plane wave type
MORE FAR-FIELD POSTPROCESSING VARIABLES

Maximum variables for directivity, gain, and realized gain have been added. These areavailable for global evaluation without plotting a 3D far-field pattern, when theselection for the far-field calculation feature is spherical for 3D and circular for 2D
axisymmetric components, and its center is on the origin.
ELECTRICALLY THICK LAYER IN TRANSITION BOUNDARY CONDITION

The electrically thick layer option makes the two domains adjacent to the transition
boundary uncoupled. The boundary performs like an interior impedance boundary
condition but the geometry no longer has to be a domain.

136 |CHAPTER 1: RELEASE NOTESFAR-FIELD ANALYSIS IN TRANSIENT STUDY

A far-field domain/calculation feature is now available in the Electromagnetic Wave,
Transient physics interface. With this feature, a wideband antenna far-field patternanalysis in the frequency domain can be obtained by performing a transient response
analysis and a time-to-frequency fast Fourier transform (FFT).
CIRCULARLY POLARIZED BACKGROUND FIELD IN 2D AXISYMMETRICCOMPONENT MODEL

A circularly polarized plane wave is available for the scattered field formulation whenmodeling with a 2D axisymmetric component. By exciting an axisymmetric scatterer
with a circularly polarized background field in a 2D axisymmetric geometry, the farfield and radar cross section (RCS) of the same scatterer in 3D, illuminated by a linearlypolarized background field, can be quickly estimated using the norm3DEfar function.
USER INTERFACE ENHANCEMENT IN PORT FEATURE

In and Outport Direction
Arrow visualization on the port feature helps to quickly identify the inport (active andexcited port) and outport (passive and listener port) through the Graphics window.
The arrow points in the direction of power flow. An excited port presents an inward
arrow on the port boundary while a listener port has an outward arrow on the port
boundary. Lumped ports support this visualization feature.

Numeric TEM with Voltage Drop Direction
When numeric-type ports are analyzed by boundary mode analysis, degenerated
modes make it problematic to compute S-parameters accurately. The voltage drop
direction represents the red arrow tangential to the port boundary, and it fixes the portmode field polarization. The direction can be changeable by clicking the Toggle Voltage
Drop Direction button in the Settings window of the Integration Line for Voltage node,
which is a subnode to the numeric TEM-type port feature.
MORE FEATURES FOR TIME EXPLICIT PHYSICS INTERFACE

Perfect electric conductor (PEC), perfect magnetic conductor (PMC), and surface
current density now can be applied on interior boundaries as well. A lumped port isadded and it calculates S-parameters. Lumped ports can only be added on exterior
boundaries.

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NEW STUDY SEQUENCES IN THE MODEL WIZARD FOR ONE-WAY
COUPLED MULTIPHYSICS

When adding an electromagnetic heating multiphysics interface like Microwave
Heating in the Model Wizard, there are now two new study sequences available. The
Sequential Frequency-Stationary study first solves a frequency-domain equation forelectromagnetics and then uses the electromagnetic heat source as a source term whensolving a subsequent stationary heat transfer equation. The Sequential FrequencyTransient study first solves a frequency-domain equation for electromagnetics and thenuses the electromagnetic heat source as a source term when solving a subsequent timedependent heat transfer equation. For both study sequences, it is assumed that theelectromagnetics problem does not depend on the computed temperature
distribution.
THE REFRACTIVE INDEX ELECTRIC DISPLACEMENT FIELD MODEL NOWALLOWS INPUT OF FULLY ANISOTROPIC TENSORSWhen the Refractive index option is selected for the Electric displacement field list in
wave equation features, it is now allowed to input a fully anisotropic tensor. A matrixmatrix multiplication is used to transform this refractive index tensor to the relative
permittivity tensor.
DEFAULT COLOR TABLE FOR DEFAULT PLOTS CHANGED TORAINBOWLIGHT

To improve legibility of the default black texts that appear on low-level parts of a plot,
the default color table has been changed to RainbowLight for default plots. Now, thelow-level parts are rendered with a lighter blue tone, improving the legibility.
NODAL CONSTRAINTS AND EXPLICIT-ORTHONORMAL NULL-SPACEFUNCTION

The default constraint type is now Nodal instead of the previous Elemental. This allows
more efficient constraint elimination through the use of the explicit-orthonormal nullspace function.

New and Updated Models in Version 5.4
TRANSIENT ANALYSIS OF A PRINTED DUAL-BAND STRIP ANTENNA

A wideband antenna study, such as S-parameter and far-field pattern analyses, can beobtained by performing a transient response analysis and a time-to-frequency fast
Fourier transform (FFT). This model runs a time-dependent study first and then138 |CHAPTER 1: RELEASE NOTEStransforms the dependent variable, the magnetic vector potential A, and a voltage
signal at a lumped port from the time domain to the frequency domain. S-parametersand far-field radiation data is generated from the frequency domain data. The
computed S-parameters shows two resonance in the given frequency range, as
expected for this dual-band antenna design
STUDY OF A DEFECTIVE MICROSTRIP LINE VIA FREQUENCY-TO-TIMEFFT ANALYSIS

While transient analyses are useful for time domain reflectometry (TDR) to handle
signal integrity (SI) problems, many RF and microwave examples are addressed using
frequency domain simulations generating S-parameters. However, from the frequency
domain data, it is difficult to identify sources for this signal degradation. This example
simulates a microstrip line in the frequency domain with a couple of line width
discontinuities and performs frequency-to-time fast Fourier transform. The computed
results help to identify the physical discontinuities and impedance mismatches on thetransmission line by analyzing the signal fluctuation in the time domain.
UPDATED MODELS

Application Library path for the updated examples using parts from the RF Part
Library:• RF_Module/Antennas/double_ridged_horn_antenna• RF_Module/Couplers_and_Power_Dividers/branch_line_coupler• RF_Module/Couplers_and_Power_Dividers/wilkinson_power_divider• RF_Module/Transmission_Lines_and_Waveguides/sma_connectorized_gcpw

Application Library path for the updated examples using the Isosurface plot type:• RF_Module/Antennas/biconical_frame_antenna• RF_Module/Antennas/dipole_antenna• RF_Module/Antennas/helical_antenna• RF_Module/Antennas/log_periodic_antenna• RF_Module/Antennas/vivaldi_antenna• RF_Module/EMI_EMC_Applications/airplane_antenna_crosstalk• RF_Module/Filters/cascaded_cavity_filter• RF_Module/Filters/cylindrical_cavity_filter_evanescent

Application Library path for the updated example on calculating an axial ratio:• RF_Module/Antennas/helical_antenna

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Application Library path for the updated example on visualizing material properties:• RF_Module/Microwave_Heating/sar_in_human_head

Application Library path for the updated example on using an array factor:• RF_Module/Antennas/microstrip_patch_antenna_inset

140 |CHAPTER 1: RELEASE NOTESRotordynamics Module
New Functionality in Version 5.4
DISK PROPERTIES FROM GEOMETRICAL DIMENSION

When adding a circular Disk in the Beam Rotor interface, you can now also computethe mass properties from geometrical size and mass density.
FLOATING RING BEARING

A new Floating Ring Bearing model has been added to the Hydrodynamic Bearing
interface. In a floating ring bearing, an extra ring is placed between the bearing andjournal surfaces so that two lubrication films are formed. These films are connected byoil channels in the ring. The ring can be either fully floating or semifloating.
ROTOR COUPLING

The new Rotor Coupling feature in the Beam Rotor and Solid Rotor interfaces allows
for shafts that are not coupled in all directions. This makes it possible to model, forexample, spline couplings. You can also model connections between shafts with acertain flexibility.
MISALIGNMENT

You can now model misalignment in bearings by adding the new Misalignment
subnode. It is available for:• Journal Bearing, Thrust Bearing, Radial Roller Bearing, and Rotor Coupling in the Solid
Rotor interface.
• Journal Bearing, Thrust Bearing, Radial Roller Bearing, and Rotor Coupling in the Beam
Rotor interface.
• Hydrodynamic Journal Bearing, Hydrodynamic Thrust Bearing, and Floating Ring Bearing
in the Hydrodynamic Bearing interface.
Both parallel and angular misalignment can be modeled.
TILT ANGLE IN TILTED PAD BEARINGThe pads in tilted pad bearings are usually free to tilt about a pivot point. In theequilibrium state, the tilt angle is such that the net moment on the pad due to thepressure in the fluid film is zero. It is now possible to compute the equilibrium tilt

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angle automatically by performing nonlinear iterations to achieve moment
equilibrium.
FOUNDATIONS FOR ROLLER BEARINGSFoundation for the roller bearings have been added. In the Foundations section in thesettings for Radial Roller Bearing, you can now choose to use Fixed, Moving, or Flexible
foundation. Using this functionality, it is possible to model stator-rotor assemblies
connected through roller bearings.
STATIC EQUILIBRIUM OF JOURNAL

You can now compute the equilibrium position of the journal in the bearing for a given
static load. This is available for Hydrodynamic Journal Bearing and Floating Ring Bearing
in the Hydrodynamic Bearing interface.
ROLLER FORCE DISTRIBUTION

You can now visualize the roller force distribution in roller bearings on the boundaries
connected to the inner race for both the Solid Rotor and Multibody Dynamics
interfaces. The variables, which are available in the results menus, have names likerotsld.rrb1.fbx, rotsld.rrb1.fby, and so on.

New Models in Version 5.4
RECIPROCATING ENGINE WITH HYDRODYNAMIC BEARINGS

A single cylinder reciprocating engine supported on hydrodynamic bearings is studied.
A starting torque is applied to bring the engine to the required rpm. The loading
torque is switched on once the engine picks up speed. After the start-up, the engine
operates on its own, driven by the cylinder pressure. The engine assembly is modeledusing the Multibody Dynamics interface in the Multibody Dynamics Module, and thebearing is modeled using the Hydrodynamic Bearing interface in the Rotordynamics
Module. A Solid-Bearing Coupling multiphysics coupling is used. The results include
stress in the crankshaft and foundation, pressure in the bearings, engine speed
variation, generated power, brake horsepower, and orbit of the shaft in the bearing.
TURBOCHARGER SUPPORTED ON FLOATING RING BEARINGSIn this model, a turbocharger supported on two floating ring bearings is studied. The
film forces acting on the ring cause it to rotate within the bearing. In a steady state, thering rotates at a constant angular speed, and the torque on the ring due to the innerand outer films is balanced.The Beam Rotor interface is used to model the142 |CHAPTER 1: RELEASE NOTES

turbocharger rotor, which is coupled with the floating ring bearing using multiphysics
couplings. The inner and outer films in the floating ring bearings are connected by six
channels in the ring. The results include stress in the rotor, pressure distribution in the
bearing, speed variation of the ring, total moment on the ring, and flow rate throughthe ring channels.
EFFECT OF BEARING MISALIGNMENT ON ROTOR VIBRATIONIn this example, a rotor supported on two hydrodynamic bearings is analyzed. An
eccentric disk located between the two bearings causes the rotor to whirl. One of the
bearings is misaligned with the axis of the rotor. The Beam Rotor with Hydrodynamic
Bearing interface in the Rotordynamics Module is used for the combined simulationof rotors and bearings. The analysis is performed for two cases, first without
misalignment and then including the misalignment. Results for both cases arecompared to understand the effect of the misalignment. Some of the results are theorbit of the disk, frequency spectrum of the rotor response at the disk, and pressure
distribution in the bearings.
STEP THRUST BEARINGIn this tutorial model, a six-step thrust bearing is analyzed. A step thrust bearing
consists of a stepped bearing surface on which the end of the shaft rotates. The entire
assembly is submerged in a lubricant. The shaft collar is assumed to be spinningwithout any axial motion in the bearing. The results include pressure distribution in
the bearing, pressure variation in radial and circumferential directions of the pad, andload-carrying capacity of the bearing.

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Semiconductor Module
New Functionality in Version 5.4
SCHRÖDINGER-POISSON EQUATION

A new Schrödinger-Poisson Equation multiphysics interface is introduced to create abidirectional coupling between an Electrostatics physics interface and a Schrödinger
Equation physics interface to model charge carriers in quantum-confined systems. The
electric potential from the Electrostatics interface contributes to the potential energy
term in the Schrödinger Equation interface. A statistically weighted sum of theprobability densities from the eigenstates of the Schrödinger Equation interface
contributes to the space charge density in the Electrostatics interface. All spatial
dimensions (1D, 1D axial symmetry, 2D, 2D axial symmetry, and 3D) are supported.
A dedicated Schrödinger-Poisson study type is available for automated generation ofself-consistent iterations in the solver sequence. A new benchmark model, SelfConsistent Schrödinger-Poisson Results for a GaAs Nanowire, demonstrates theusage of this new feature.
TRAP-ASSISTED SURFACE RECOMBINATION

A new boundary condition, Trap-Assisted Surface Recombination, replaces the Surface
traps check box in the features Insulation, Thin Insulator Gate, and Insulator Interface.
Unlike the old check box, which only allows one option of explicit traps, the newboundary condition has both options of SRH recombination and explicit traps like its
domain counterpart (the Trap-Assisted Recombination domain condition). In
addition, the new boundary condition is extended to include Schottky contacts. A
problem in the FEM formulation (surface charge has no effect) has been fixed.
WKB TUNNELING MODEL

A new tunneling feature based on the WKB approximation is now available to accountfor the additional current densities for the carrier transport across a heterojunction ora Schottky barrier via quantum tunneling. A new benchmark model, Heterojunction
Tunneling, demonstrates the usage of this new feature.

144 |CHAPTER 1: RELEASE NOTESHETEROJUNCTIONS (THERMIONIC EMISSION OPTION) AND SCHOTTKYCONTACTS

A new section, Extra Current Contribution, is now available for adding a user-defined
extra contribution or for using the new WKB Tunneling Model mentioned above.
HETEROJUNCTIONS

For the Thermionic Emission option, a single value of A* (Richardson's coefficient) is
computed by picking the smaller effective mass between the two sides for thethermionic emission current densities on both sides, so that the total current density
consistently cancels to zero at equilibrium.
INSULATOR TUNNELINGThe variable for the perpendicular electric field in the insulator (semi.E_ins) is now
available for the user-defined tunneling type, making it more convenient to define thetunneling current density.
STABILITY IMPROVEMENTS

The Fletcher mobility model and the SRH, Auger, and Direct recombination models
have been improved by incorporating nonnegative carrier concentration values in theformulation.
TERMINAL NAMING WHEN DUPLICATING

When duplicating or pasting metal contacts, insulated gates, or electrostatic terminals,
the duplicated entity now has a new unique terminal name. Before version 5.4, theduplicated entity had the same terminal name as the original entity.
SMALL-SIGNAL TERMINAL CURRENT

The terminal current variable for the small-signal analysis now includes thecontribution from the displacement current. This makes it convenient to compute
lumped parameters such as the differential capacitance of a biased Schottky contact.
SMALL-SIGNAL CONTINUOUS TRAPPING LEVELS

The small-signal analysis can now be performed on systems with continuous trappinglevels.
SEMICONDUCTOR EQUILIBRIUM STUDY STEP

The formulation is improved for current-driven metal contacts.

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SI SOLAR CELL MODEL

The updated model si_solar_cell_1d uses AM 1.5 solar irradiance and siliconabsorption spectra for the photogeneration rate.
HETEROJUNCTION 1D MODEL

The updated model shows 4 different ways to achieve better convergence: Study 1,
manual scaling; Study 2, inherit solution from Study 1 (same as before); Study 3,
Semiconductor Equilibrium step as initial condition; and Study 4, ramp both doping
and thermionic current from 1e-8 (doping ramp was off before). Outdated solver
tweaks (initial damping, iteration number) have been removed; comments, the model
description, and the model documentation have been updated; and labels have beenrenamed.
GAN_DOUBLE_HETEROSTRUCTURE_LED MODEL

The ramping and tweaking of initial values and solver settings have been replaced by
the Semiconductor Equilibrium study step. Solver tweaks for the current bias study
have been removed. The model description, setup comments, and model
documentation have been updated.
EEPROM MODEL

Study 1 has been changed to the default solver and manual scaling for better
convergence (the model had been using the highly nonlinear Newton setting and thenbarely converged).
CORRECTIONS AND BACKWARD COMPATIBILITY• The nonradiative recombination heat source is corrected with a minor offset of(3/2)kT. This is a very small correction, since the majority of the heat source iscontributed by the band gap energy, which is much larger than kT.
• The gan_double_heterostructure_led model has changed the InGaN thickness
from 5 nm to 50 nm to match reference paper.
• A Vertical height input is available for 1D axisymmetric geometries, with the default
value 1[um] (had been hard-coded to 1[m]).
• The default solver suggestion now has sparsity pattern caching turned on for both
stationary and time-dependent studies and all formulations.
• For the Schottky Contact, the input for the metal work function is hidden for userdefined barrier heights.
• For the Schrödinger Equation interface, periodic boundary conditions are available
for 2D axially symmetric geometries.

146 |CHAPTER 1: RELEASE NOTESNew Models in Version 5.4
SELF-CONSISTENT SCHRÖDINGER-POISSON RESULTS FOR A GAAS
NANOWIRE

This benchmark model simulates a GaAs nanowire using the self-consistent
Schrödinger-Poisson theory to compute the electron density and the confining
potential profiles. The predefined Schrödinger-Poisson multiphysics coupling feature
is combined with the dedicated Schrödinger-Poisson study type to provide a
streamlined procedure for model setup and automated creation of self-consistent
iterations with tunable parameters for optimizing the convergence under different
conditions. The computed electron density and confining potential profiles compare
well with the figures in the reference paper with both profiles reproducing the distinct
Friedel-type spatial oscillations at low temperatures.
HETEROJUNCTION TUNNELINGThis benchmark model simulates a graded heterojunction using the thermionicemission formulation for the charge transfer over the junction. It shows the additional
contribution to the current density from the quantum tunneling effect across thepotential barrier, using the WKB approximation. Even though the simulated system is
1D in nature, a 2D model is created to illustrate the procedure for simulating a moregeneral configuration. Also demonstrated is the setup of user-defined ternary material
properties. The computed I-V curves, their temperature dependence, and energy band
diagrams all agree well with results from the literature.
INTERFACE TRAPPING EFFECTS OF A MOSCAPThis tutorial compares experimental data from the literature with a COMSOLMultiphysics model of a MOSCAP with interface traps (surface states). The TrapAssisted Surface Recombination feature is used to simulate the effects of the trap
charges and the processes of carrier capturing and emitting by the traps. The effect of
the fixed charges in the gate oxide is also included. The computed values of thecapacitance and conductance as functions of the gate voltage and frequency reproduce
the qualitative behavior of the experimental data with comparable magnitudes. The
model uses the quasi-Fermi level formulation and shows how to plot quantities suchas the trap occupancy as a function of the energy.
FORWARD RECOVERY OF A PIN DIODE

This tutorial simulates the turn-on transient (forward recovery) of a simple PIN diode,based on the book “Fundamentals of Power Semiconductor Devices” by B. J. Baliga

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(p. 242, 2008 edition). The diode is current driven with a constant ramp rate of 1e9,
2e9, and 1e10 A/cm^2/sec as well as a steady-state current density of 100 A/cm^2.
The resulting time evolution of the device voltage and electron concentration compare
well to those shown in the book (Fig. 5.30–5.31). For a more sophisticated example
that includes band gap narrowing, carrier-carrier scattering, and external load circuit
elements, see the tutorial “Reverse Recovery of a PIN Diode”.
REVERSE RECOVERY OF A PIN DIODE

This tutorial simulates the turn-off transient (reverse recovery) of a simple PIN diodewith an inductive load, loosely based on the book “Fundamentals of Power
Semiconductor Devices” by B. J. Baliga (p. 256, 2008 edition). Unlike the book,which assumes an initial constant current ramp rate followed by an abrupt bottoming
out of the device voltage at the supplied reverse voltage, this model uses the circuit
capability of COMSOL Multiphysics to simulate the inductive load with a flyback
diode in a more realistic fashion. The resulting time evolution of the current, voltages,
and carrier concentrations compare well to those shown in the book (Fig. 5.42–5.45).

148 |CHAPTER 1: RELEASE NOTESStructural Mechanics Module
New Functionality in Version 5.4
NEW SHELL INTERFACE IN 2D AXISYMMETRY

The Shell interface is now available in a 2D axisymmetric geometry. The formulationand functionality are essentially the same as in its 3D counterpart. Also, the Solid-Shell
Connection multiphysics coupling has been extended to 2D axisymmetry.
CHANGED INPUT OF THICKNESS AND OFFSET IN THE SHELL INTERFACE

The input of thickness and offset properties has been moved to a separate node named
Thickness and Offset. One such node is always present in the model, and you can add
more as required.
This means that the old input of these properties in the interface settings, as well as the
Change Thickness node, has been removed. Old models are automatically converted touse the new syntax.
CHANGES IN SYMMETRY AND ANTISYMMETRY FOR 2D AXISYMMETRIC
INTERFACES

In the 2D axisymmetric version of the Solid Mechanics and Membrane interfaces, thenodes Symmetry and Antisymmetry are now obsolete. They have been replaced by theSymmetry Plane node. The reason is that the only possible true symmetry in an
axisymmetric model is with respect to a cut perpendicular to the Z-axis. The oldfeatures allowed unphysical constraints.
RESPONSE SPECTRUM ANALYSIS

Response spectrum analysis, which is used for estimating the peak response of short,nondeterministic, dynamic events, has been added. It can be used for any combinationof structural mechanics interfaces in 2D and 3D. A new node, Response Spectrum, hasbeen added under Defintions>Variable Utilities. Here, some variables are added, andyou can also automate the setup of a special study sequence. Most of the settings forresponse spectrum evaluation are done in the new Response Spectrum 2D and Response
Spectrum 3D data sets.
There are several modal combination methods, such as SRSS, CQC (der Kiureghian),absolute sum, ten percent method, grouping method, and double sum (Rosenblueth).

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Four spatial combination methods are available: SRSS, 100-40-40, CQC3, and SRSS3.
It is also possible to separate periodic and rigid modes using the Gupta and LindleyYow methods and to add a static correction for mass not represented by the
eigenmodes.
NEW MODAL SUPERPOSITION STUDY TYPES

Two new predefined study sequences for modal superposition have been added: Time
Dependent, Prestressed, Modal and Frequency Domain, Prestressed, Modal. In both cases,
three study steps are generated, where the first one is a stationary step in which theprestress state used for the subsequent eigenfrequency computation is determined.
RENAMED STUDY TYPES

Some study types have been renamed in order to get a more consistent naming:• Frequency Domain Modal is now Frequency Domain, Modal• Time Dependent Modal is now Time Dependent, Modal• Prestressed Analysis, Eigenfrequency is now Eigenfrequency, Prestressed• Prestressed Analysis, Frequency Domain is now Frequency Domain, Prestressed
PARTICIPATION FACTORS FOR EIGENFREQUENCY STUDIESWhen you add an Eigenfrequency study from the Add Study window, a Participation
Factors node is now automatically added under Definitions, as long as there is at least
one structural mechanics physics interface in the model. You will thus always haveaccess to the participation factor variables after running such a study.
MATERIAL ACTIVATION

It is now possible to activate a material in a stress-free state using the new Activation
subnode under Linear Elastic Material in the Solid Mechanics and Membrane interfaces.
A user-defined logical expression is used for the activation. The same feature can also
be used to remove material. Typical applications are various types of manufacturing
processes where material is added.
HOMOGENIZATION OF PERIODIC MATERIALS

Inhomogeneous materials can often be represented by a unit cell that is assumed to bepart of a periodic structure. This is sometimes called a representative volume element

150 |CHAPTER 1: RELEASE NOTES(RVE). The new Cell Periodicity feature in the Solid Mechanics interface provides
several options for analyzing such unit cells:• Automatic computation of equivalent homogenized anisotropic material properties(stiffness, compliance, thermal expansion), which can be accessed as a Global
Material.
• Computation of the local stresses and strains in the unit cell, given external average
stress and strain fields.
• Computation of free thermal or hygroscopic expansion of the unit cell, given
average temperature or moisture concentration.
BURGERS VISCOELASTIC MODEL

One more built-in viscoelastic model has been added: the Burgers model. As with theother viscoelastic models, it is accessed by adding a Viscoelasticity subnode under the
Linear Elastic Material.
VOLUME REFERENCE TEMPERATURE

A new concept, volume reference temperature, has been introduced. It serves two
purposes: It replaces the earlier strain reference temperature for thermal expansion,and it is the temperature at which the mass density is computed. These two phenomena
are physically related to each other, and the default is to use the same value, defined asa Common model input. For the mass density, the concept is new, and is used to avoid
violations of mass conservation. For thermal expansion, the default location, where
you specify the strain-free temperature, has moved from the Thermal Expansion nodeor Thermal Expansion multiphysics coupling to Common model input.
When you open an old model, the value of the strain reference temperature isconverted to a User Defined volume reference temperature.
UTILITY FUNCTIONS FOR EXTERNAL MATERIALSWhen programming your own constitutive relations using the external materials
functionality, there are several operations for which there is a recurring need. Examplesof this are various tensor operations, computation of principal values and orientations,and matrix inversion. There is now a library of utility functions that covers many
common operations you would employ when programming material models for solidmechanics.

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TIME STEP PASSED TO EXTERNAL MATERIALSThe time or parameter step is now passed as an argument to the material function whenusing the General Stress-Deformation Relation socket.
NEW SETTINGS FOR MIXED FORMULATION

In earlier versions, a mixed (displacement-pressure) formulation could be activatedusing the Nearly incompressible material check box in a material model. It has been
replaced by the Use mixed formulation drop-down list with the following three choices:
None, Pressure formulation, and Strain formulation. The pressure formulation is thesame mixed formulation as was used before, while the strain formulation is new.
Instead of a pressure, the volumetric strain is used as an extra degree of freedom.
NEW FLUID-STRUCTURE INTERACTION INTERFACES

The fluid-structure interaction (FSI) couplings have been extended to allow
interaction with shells and membranes. There are now six entry points for FSI under
Fluid Flow in the Add Physics window:• Fluid-Solid Interaction• Fluid-Solid Interaction, Fixed Geometry• Fluid-Shell Interaction• Fluid-Shell Interaction, Fixed Geometry• Fluid-Membrane Interaction• Fluid-Membrane Interaction, Fixed Geometry
If you also have a license for the Multibody Dynamics Module, you will find two more
entry points:• Fluid-Multibody Interaction• Fluid-Multibody Interaction, Assembly
The Fluid-Structure Interaction, Fixed Geometry multiphysics coupling present inprevious releases is now obsolete. It has been merged with an updated Fluid-StructureInteraction multiphysics coupling. This makes it easier to switch between the two
formulations. In the current version, the only difference lies in whether a Deforming
Domain is active on a fluid domain or not.
Old models, where you used Fluid-Structure Interaction, Fixed Geometry, are notchanged. You are, however, advised to update to the new type of modeling.

152 |CHAPTER 1: RELEASE NOTESRIGID DOMAIN IN 2D AXISYMMETRY

The Rigid Domain material model is now available in 2D axisymmetry. It has only asingle degree of freedom: the axial translation.
RIGID CONNECTOR FOR EDGES AND POINTSThe selection in a Rigid Connector can now be a combination of boundaries, edges, andpoints. It is now also possible to add a rigid connector at the edge and point levels, aslong as there are no higher-order geometrical objects in the selection.
FLEXIBLE FORMULATION OF RIGID CONNECTOR

There are now two formulations of the Rigid Connector feature: Rigid and Flexible. In
the default formulation, all the selected boundaries, edges, and points behave as if they
were connected by a common rigid body. In some cases, this gives an unwanted
stiffening or unrealistic local stresses. You can then switch to a flexible formulation
where the constraint is applied only in an average sense. The flexible formulation isavailable only for a rigid connector with a pure boundary selection and not when theselection also contains edges or points.
DRILL ADDED TO BOLT PARTS

In the Bolts section of the Part Libraries, there are now geometries that, in addition to
the bolt itself, contain a domain intended to be used as a “drill” when building thegeometry. This is particularly useful when working with the Bolt Thread Contact
feature.
TABULAR OUTPUT OF EIGENFREQUENCIES

When running an Eigenfrequency study, a table containing the natural frequencies,
modal damping, and quality factors is now generated by default.
SPRING AND REACTION FORCES

A new reaction force variable, containing the sum of reaction forces from constraints
and reaction forces from spring foundations, has been added to all structural
mechanics physics interfaces. The variables, which are available in the result menus, arecalled Total reaction force and have component names like solid.RFtotalx. If there
are spring foundations in your model, you will find the forces under the category Springand Damping forces in the result menus.
REACTION-FREE SYMMETRY CONDITION

The symmetry conditions in the structural mechanics interfaces have been extended toaccount for cases where the symmetry plane is allowed to translate in the direction of

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its normal rather than being a fixed plane. The main application is for use as a boundary
condition in truncated structures having no net reaction force. In the new section
Normal Direction Condition in the settings for the Symmetry node, you can adjust the
behavior of this boundary condition. There are four different options: No displacement(the default), Free displacement, Prescribed force, and Prescribed displacement.
ROLLER CONDITION WITH ANALYTICAL NORMAL ORIENTATION

The default roller constraint acts along a normal to the selected boundaries. The
normal is computed numerically. For a certain mesh node, this direction is kept
constant during the analysis, so it cannot represent finite sliding on a curved boundary.
You can now, however, prescribe that the boundary slides on an analytical surface.
There are two situations where you may need to do this:• The geometry or mesh representation of the actual boundary is imperfect. This canlead to unexpected locking of the deformation, since the computed normals do nothave the intended directions.
• In a geometrically nonlinear analysis, the use of an analytical surface makes it
possible to also model finite sliding along curved boundaries.
You can now, in the settings in the Roller node, select a Normal orientation, which canbe either Automatic, Plane, Cylinder, or Sphere.
IMPROVED PRESCRIBED ROTATION IN THE BEAM INTERFACE

The settings for prescribed rotations in the Prescribed Displacement/Rotation node in
the Beam interface have been changed. The new representation is the same as in thecorresponding node in the Shell interface, making it easier to prescribe finite rotations
in a geometrically nonlinear case. In a model created in an earlier version, the settings
are converted to the new style automatically.

New Models in Version 5.4
EARTHQUAKE ANALYSIS OF A BUILDINGThis example shows how to verify the integrity of a structure exposed to an earthquake
using response spectrum analysis. The building is modeled as a steel frame using beam
elements. Displacements and stresses are computed.
SHOCK RESPONSE OF A MOTHERBOARD

Electronic equipment often needs to be certified to function after having been
subjected to a specified shock load. In this example, the effect of an 11-ms half sine154 |CHAPTER 1: RELEASE NOTESshock with 50-g amplitude on a circuit board is investigated using response spectrum
analysis. Results are compared with a full time-domain solution.
CONNECTING BEAMS AND SOLIDS

This example demonstrates the use of the Solid-Beam Connection multiphysics couplingto create transitions between the Solid Mechanics and Beam interfaces. Two different
connection types are discussed, and a comparison of the stress distributions at thetransition is made.
PRESTRESS OF MAIN BEARING CAP BOLTS

This example shows how to model prestressed bolts. The bolt geometry is taken fromthe Part Libraries. For comparison, one of the bolts is modeled using a thread contact
formulation, whereas the other bolt is connected to the bolt hole by a pure continuity
condition. The reduced stiffness in the threaded part of the bolt is taken into accountby a reduction of the stiffness of the material.
MICROMECHANICAL MODEL OF A COMPOSITEIn this example, a simplified micromechanical model of a unit cell with periodic
boundary conditions is analyzed. The homogenized elastic and thermal properties ofa composite material are computed based on individual properties of the fiber andmatrix. A comparison of numerical values is made against values obtained from theRule of Mixture.
SPHERICAL CAP WITH CENTRAL POINT LOAD

This benchmark studies the nonlinear deformation of a spherical cap subjected to apoint load at center using 2D axisymmetric Solid Mechanics and Shell interfaces. The
results from the Shell interface are compared with the Solid Mechanics interface as wellas with analytical results given in the benchmark for different discretizations.

Backward Compatibility with Version 5.2
The friction slip velocity is no longer defined as a dependent variable. When runninga model using the COMSOL API, you will need to remove the reference to thisvariable in the solver settings. The friction slip velocity is usually defined as<comp>_<solid>_vslip_<pairname>, where <comp> is the tag of the component,<solid> is the tag of the Solid Mechanics physics interface where the Friction node isdefined, and <pairname> is the name of the contact pair.

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Backward Compatibility with Version 4.3b
• If an old model using the Beam interface is opened, the Euler-Bernoulli formulation
is used. The Beam Formulation selection is still shown but cannot be changed from
Euler-Bernoulli. If Advanced Physics Options is enabled, then the new section
Backward Compatibility is shown. If you clear the Use pre 4.4 formulation check box,
then the new formulation is used. Doing this enables the use of Timoshenko beams,
but you must manually handle solver settings like segregation and scaling. This
legacy option does not support beams mixed with solids or shells in cases where thesame names for degrees of freedom were used in both physics interfaces.
• For models using mechanical contact, plot expressions are not updated when you
open an old model where the pair names have been edited manually. Also, opening
an old model where a pair name has been manually edited might affect the solver
configuration. It is recommended that you regenerate a new default solver
configuration.

Backward Compatibility with Version 4.3a
• When using version 5.2a, in the Solid Mechanics interface, the property
ControlsSpatialFrame from version 4.3a no longer exists, and COMSOLMultiphysics now always assumes that the displacements control the spatial frame.
Remove all lines setting the value of ControlsSpatialFrame. See Support
Knowledge Base article 1156.
• When opening old models that include contact, the penalty factor control is set toUser defined and the contact normal penalty factor is set to the expression used in
the model.

156 |CHAPTER 1: RELEASE NOTES

Subsurface Flow Module
New Functionality in Version 5.4
Updated formulation for the Flux and No Flux nodes included in the Transport of
Diluted Species and Transport of Diluted Species in Porous Media interfaces.
- The flux relative to the convective flux is prescribed instead of the total flux.
- The new formulation implies that the nodes can be used on a moving meshgeometry without compensating for the boundary velocity.
- Updated equation display for governing equations and boundary conditions.
Equations updated to be formulated in terms of the flux relative to the convective
flux.
There is an updated formulation for the Gravity feature included in Darcy’s Law,
Fracture Flow, and Richards’ Equation interfaces.
There is a new formulation for the Symmetry node included in the Two-Phase Darcy’s
Law interface.
NEW PHASE TRANSPORT INTERFACES

The new Phase Transport in Porous Media interface is used to simulate the transport ofmultiple immiscible phases through a porous medium. The interface solves for the
averaged volume fractions (saturation) of the phases without tracking the interface
between the different phases. Microscopic interfacial effects are taken into accountthrough capillary pressure functions.
The new Multiphase Flow in Porous Media interface combines the functionality of theDarcy’s Law and Phase Transport in Porous Media interfaces. This multiphysics
interface is intended to model flow and transport of multiple immiscible phases in a
porous medium.
The new Phase Transport interface is used to simulate the transport of multiple
immiscible phases in free flow. This interface solves for the averaged volume fractionsof the phases in laminar or creeping flow, without tracking the interface between them.

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New Models in Version 5.4
TWO-PHASE FLOW IN A POROUS MEDIUM: BUCKLEY-LEVERETT MODEL

This benchmark models two-phase flow in a porous medium in 1D, where the flow
can be analytically described by the Buckley-Leverett equation.
TWO-PHASE FLOW OVER A LOW PERMEABLE LENSThis example demonstrate two-phase flow in a porous medium that contains a low
permeable lens. The heavier phase infiltrates the porous medium, so the low permeablelens is infiltrated only when a critical saturation is reached.
RESERVOIR WITH HORIZONTAL WELLSThis example models a thin oil reservoir with two horizontal wells. The reservoir
contains two phases: water and oil. The oil is recovered by injecting water through thebottom well, so the oil production rate and the water-oil production ratio over time
are computed.

Backward Compatibility with Version 5.3a and Earlier
NO FLUX FORMULATION

The formulation of the No Flux feature has been changed in the Transport of Diluted
Species and Transport of Diluted Species in Porous Media interfaces in version 5.4 sothat the flux relative to the convective flux is set to zero. The new formulation is used
when opening a model from a previous session. In the previous formulation, the total
flux was set to zero.

158 |CHAPTER 1: RELEASE NOTESWave Optics Module
New Functionality in Version 5.4
TRANSITION BOUNDARY CONDITION FOR THE ELECTROMAGNETICWAVES, BEAM ENVELOPES INTERFACE

This new feature allows modeling of electrically thin layers using a boundary feature;
thereby, the user does not need to add a domain mesh. This will be useful for modelingthin metallic layers in, for instance, mirror applications. However, this special
implementation for the Electromagnetic Waves, Beam Envelopes interface also works
fine for thin dielectric layers, like antireflection coatings.
IMPEDANCE BOUNDARY CONDITION FOR THE ELECTROMAGNETICWAVES, BEAM ENVELOPES INTERFACE

This feature allows truncation of the simulation domain at an interface between two
different material domains. The exterior material could be a highly conducting
material, like a metal, but for this special implementation for the Electromagnetic
Waves, Beam Envelopes interface, it could also be a dielectric layer, like a glass
substrate.
SLIT PORTS FOR THE ELECTROMAGNETIC WAVES, BEAM ENVELOPESINTERFACE

A slit port is used on an interior boundary for exciting the simulation domain with anincident wave and then absorbing scattered waves matching the port mode field. A
domain-backed slit port is normally backed by a perfectly matched layer (PML) thatabsorbs the remaining part of the scattered radiation that was not absorbed by the
port. A PEC-backed slit port has a regular port on one side, and on the other side aperfect electric conductor (PEC) boundary condition is applied.
Domain-backed slit ports can be good to use when exciting the domain with aGaussian beam, as the reflected Gaussian beam will not be perfectly absorbed by the
port. However, together with the backing PML domain, almost all reflected radiation
can be absorbed.

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NEW STUDY SEQUENCES IN THE MODEL WIZARD FOR ONE-WAY
COUPLED MULTIPHYSICS

When adding an electromagnetic heating multiphysics interface, like the Laser Heatinginterface, in the Model Wizard, there are two new study sequences available. The
Sequential Frequency-Stationary study first solves a frequency-domain equation forelectromagnetics and then uses the electromagnetic heat source as a source term whensolving a subsequent stationary heat transfer equation. The Sequential FrequencyTransient study first solves a frequency-domain equation for electromagnetics and thenuses the electromagnetic heat source as a source term when solving a subsequent timedependent heat transfer equation. For both study sequences, it is assumed that theelectromagnetics problem does not depend on the computed temperature
distribution.
THE REFRACTIVE INDEX ELECTRIC DISPLACEMENT FIELD MODEL NOWALLOWS INPUT OF FULLY ANISOTROPIC TENSORSWhen the Refractive index option is selected for the Electric displacement field list in
wave equation features, it is now possible to input a fully anisotropic tensor. A matrixmatrix multiplication is used to transform this refractive index tensor to the relative
permittivity tensor.
DEFAULT COLOR TABLE FOR DEFAULT PLOTS CHANGED TORAINBOWLIGHT

To improve legibility of the default black texts appearing on low-level parts of the plot,
the default color table has been changed to RainbowLight for default plots. Now, thelow-level parts are rendered with a lighter blue tone, improving the legibility.
UNIFORM ANTENNA ARRAY FACTOR FUNCTION

It is possible to evaluate the radiation pattern of an antenna array quickly from a single
antenna radiation pattern by using an asymptotic approach such as multiplying the farfield of a single antenna with a uniform array factor.

160 |CHAPTER 1: RELEASE NOTES

3D FAR-FIELD AND RCS FUNCTIONS FROM 2D AXISYMMETRICCOMPONENT MODEL

2D axisymmetric modeling becomes more useful for a quick estimation of the far-field
response of the equivalent 3D model by utilizing new far-field functions. 3D far-fieldnorm functions in 2D axisymmetric geometry are available in these cases:• Antenna models using circular port excitation with a positive azimuthal mode
number• Scattered field analysis excited by the predefined circularly polarized plane wave type
MORE FAR-FIELD POSTPROCESSING VARIABLES

Maximum variables for directivity, gain, and realized gain have been added. These areavailable for global evaluation without plotting a 3D far-field pattern, when theselection for the far-field calculation feature is spherical for 3D and circular for 2D
axisymmetric components and its center is on the origin.
ELECTRICALLY THICK LAYER IN TRANSITION BOUNDARY CONDITION

The electrically thick layer option makes the two domains adjacent to the transition
boundary uncoupled. The boundary performs like an interior impedance boundary
condition, but the geometry no longer has to be a domain.
CIRCULARLY POLARIZED BACKGROUND FIELD IN 2D AXISYMMETRICCOMPONENT MODEL

A circularly polarized plane wave is available for the scattered field formulation whenmodeling with a 2D axisymmetric component. By exciting an axisymmetric scatterer
with a circularly polarized background field in a 2D axisymmetric geometry, the farfield and radar cross section (RCS) of the same scatterer in 3D, illuminated by a linearlypolarized background field, can be quickly estimated using the norm3DEfar function.
GUI ENHANCEMENT IN PORT FEATURE

Input and Output Direction
Arrow visualization on the port feature helps to quickly identify inport (active andexcited port), and outport (passive and listener port) through the Graphics window.
The arrow points in the direction of power flow. An excited port presents an inward
arrow on the port boundary while a listener port has an outward arrow on the port
boundary.

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MORE FEATURES FOR TIME-EXPLICIT PHYSICS INTERFACE

Perfect electric conductor (PEC), perfect magnetic conductor (PMC), and surface
current density now can be applied on interior boundaries.
NODAL CONSTRAINTS AND EXPLICIT-ORTHONORMAL NULL-SPACEFUNCTION

The default constraint type is now Nodal instead of the previous Elemental. This allows
more efficient constraint elimination through the use of the explicit-orthonormal nullspace function.

New and Updated Models in Version 5.4
OPTICALLY ANISOTROPIC WAVEGUIDEIn this model, a modal analysis is performed while parametrically sweeping the lengthof a waveguide from 0.5 μm to 4 μm to derive the dispersion curve for the anisotropic
core. Both transverse and longitudinal anisotropy are considered in two separate
modeling steps.
FOCUSING LENS

Optical lenses of millimeter size cannot easily be analyzed with the Electromagnetic
Waves, Frequency Domain interface on standard workstations due to the large numberof mesh elements required.
This model explains how the Electromagnetic Waves, Beam Envelopes interface can beused to analyze a plano-convex lens with a 1-mm focal length. The results arecompared with the Fresnel diffraction formula. The two results agree very well.
UPDATED MODELS

Application Library path for model using the new Transition boundary condition• Wave_Optics_Module/Optical_Scattering/beam_splitter

Application Library path for model using the new Impedance boundary condition• Wave_Optics_Module/Verification_Examples/fresnel_equations

New study in the Directional Coupler model using two copropagating modes• Wave_Optics_Module/Waveguides_and_Couplers/directional_coupler

162 |CHAPTER 1: RELEASE NOTESMaterial Library
New and Updated Material Data in Version 5.4
In version 5.4, the following improvements have been made:• Added data for several types of engineering polymers: ECTFE (polyethylene
chlorotrifluoroethylene), polyaryletherketone (PAEK), and polyvinylidene fluoride(PVDF).
• LiPb and Li17Pb83 have been added.
• Data has been added for Haynes 244, Inconel 783, Waspaloy, Alloy 901, Inconel
718, Ti-5.3Al-3Mo-1.5V, Ti-6Al-4V, and TRIP 980.
• Data has been added for Al-Zn, Bi-Sn, Sn-Zn, Cu-Sn, and Ag-Sn eutectic liquids.
• The expansion data for Haynes 242 has been refit with additional data added.
• An error in the stress-rupture data for Super 304H has been fixed.

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LiveLink™ for MATLAB ®
New Functionality in Version 5.4
LiveLink™ for MATLAB® now supports MATLAB® 2018a and 2018b.
The following sections list new and improved functionality in LiveLink™ for®
MATLAB .
USER INTERFACES

The user interfaces for mphnavigator, mphsearch, and mphmodellibrary have been
updated. They are installed as part of LiveLink™ for MATLAB® and can be started
using their respective command names. Furthermore, it is possible to install Apps
buttons available in the MATLAB® user interface for these commands using the
installer found in <comsol install dir>\mli\toolbox.
The user interface for mphnavigator shows additional information when a solution ora study is selected. The Tools>Solutions menu provides more information about solvers,
studies, and datasets as well as values of any swept parameters, time steps, oreigenvalues.
It is now possible to add a report to an existing model using mphnavigator. It is also
possible to generate reports directly from mphnavigator.
Help for nodes can be obtained in two different ways. When clicking the Help button,
help is opened using the COMSOL Documentation. When the new Help for COMSOLAPI button is clicked, help for the API methods and classes is opened for the selected
node.
PLOTTING

The function mphplot has been updated to support new plot types added to
COMSOL 5.4.
It is now possible to create plots of some nodes in the model tree (for example, physics,
geometries, and functions). Such plots are created directly by COMSOL Multiphysics
as an image and provide information that was not available previously. For showing
where the potential boundary condition is applied in the busbar model, you can use
mphplot(model.physics('ec').feature('pot1'))

164 |CHAPTER 1: RELEASE NOTESThe function mphviewselection has improved graphics for displaying overlapping
faces in 2D.
JOIN DATA SETS

The function mphinterp and other wrapper functions that access numerical data frommodels have improved support for Join data sets.
MPHLAUNCH

It is now possible to connect to a graphics COMSOL Multiphysics Server. Such a
server must be started using the -graphics argument and allows plotting by theserver.
MPHSOLINFO AND MPHSOLUTIONINFO

Both functions have been updated with improved handling of complex models; forexample, models with multiple nested parametric sweeps and time-dependent models.

Backward Compatibility with Version 5.2
The functions mpheval, mphglobal, and mphinterp, which extract numerical data,
now support complex values by default; that is, the property 'complexout' is 'on' bydefault. If you want to have the previous behavior, set 'complexout' to 'off'.

Backward Compatibility with Version 5.0• The mphint2 command: For data sets other than Solution, Particle, Cut Line,
Cut Plane, Time Integral, Time Average, Surface, and Line, the integration order
now corresponds to the element refinement. The default value is set to 4 instead of
1. This change can affect the solution in cases where the problem is not resolved wellenough.

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The COMSOL API for Use with Java®
COMSOL 5.4 API Changes
CAD IMPORT MODULE, DESIGN MODULE, AND LIVELINK PRODUCTS FORCAD CHANGESThe new fillholes property has been added for the Import function. The following
applies:• The combination of the fillholes property set to on and the knit property set tosolid is equivalent to the knit property set to solid in previous versions.
• The combination of the fillholes property set to off and the knit property set
to surface is equivalent to the knit property set to surface in version 5.3a.
• The combination of the fillholes property set to on and the knit property set tosurface is equivalent to the knit property set to surface in version 5.3 andprevious versions.
The new fillholes property has been added for the Knit function. The Knit
function with the fillholes property set to on corresponds to the Knit function inprevious versions.
ECAD IMPORT MODULE CHANGES• The properties selnetcontributetobnd, selnetcontributetodom,
selnetkeepbnd, selnetkeepdom, selnetnamebnd, selnetnamedom,selnetshowbnd, selnetshowdom, selnettagbnd, and selnettagdom have been
added to the Import function. The properties apply to the IPC-2581 and ODB++®
file types, and enable working with the selections generated for the electrical nets
found in the imported files.
• The elevation property of the Import function is now initialized when setting themanualelevation property to off. Previously, it was only initialized when setting
the filename property, and when the manualelevation property is off and thevalue of either the height or importtype properties is changed.

166 |CHAPTER 1: RELEASE NOTESCOMSOL 5.3a API Changes
PARTITION OBJECTS PROPERTIESThe keep property has been deprecated in version 5.3a. Instead, use the newproperties keepinput and keeptool. If you set keep to on, both keepinput andkeeptool are set to on. If you get the value of keep, it is on if keepinput andkeeptool are on.

COMSOL 5.3 API Changes
NEW COMPONENT SYNTAXThe geometry component is now included in the code for features that appear in acomponent. For example,
model.geom("geom1")

in earlier versions is now instead
model.component("comp1").geom("geom1")

to indicate which component the geometry belongs to. To keep the old syntax ingenerated Model Java® files, clear the Use component syntax check box under Codegeneration on the Methods page in the Preferences window. All old scripts and Java®
source code files will continue to work using the old syntax.
ECAD IMPORT MODULE CHANGES• The default value for the sellayer property of the Import function is now on.
Previously, the default was off.
• The default value for the sellayershow property of the Import function is now
all. Previously, the default was dom.

COMSOL 5.2a API Changes
AC/DC MODULE CHANGESNew Coil Feature
In the Magnetic Fields, Magnetic and Electric Fields, and Rotating Machinery,
Magnetic interfaces, a new unified Coil feature has replaced the Multi-Turn Coil feature.
The functionality of the old Multi-Turn Coil feature can be replicated by using the new
Coil feature with the Conductor model set to Homogenized Multi-Turn, but all of the

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other parameters are unchanged. The only change required is to the create statements
such as:model.physics("mf").feature().create("mtcd1","MultiTurnCoilDomain", 3);

which should be modified to:model.physics("mf").feature().create("mtcd1", "Coil", 3);model.physics("mf").feature("mtcd1").set("ConductorModel","Multi");

User-Defined Coil Geometry Subfeature Selection
In 3D models, when using a user-defined geometry for a Coil feature, the User Defined
Coil Geometry subfeature has been transformed from a boundary feature to a domainfeature. New Input and Output subnodes are used to select the coil input or output
boundaries instead. Any code setting the selection of this feature should be modified
to set the selection on the Input subfeature instead.

Relative Permeability for Magnetic Shielding in Magnetic Fields, No Current
The relative permeability parameter mur in the Magnetic Shielding feature in the
Magnetic Fields, No Currents interface is now a scalar quantity. Setting a tensor
quantity will not cause exception, but only the first component of the tensor will be
used as the value.
ACOUSTICS MODULE CHANGESThe default settings have changed for the Incident Pressure Field in the Pressure
Acoustics interfaces. Add the following line to obtain the old behavior of this featurewhen ipf1 is a subfeature to pwr1:
model.physics("acpr").feature("pwr1").feature("ipf1").
set("c", "acpr.c_c");

COMSOL 5.1 API Changes
ACOUSTICS MODULE CHANGESThe ratio of specific heats is now a material parameter. If the default value was used ina model, add the following line to the Java® file to obtain the old behavior:model.physics("cpf").feature("cpf1").set("gamma_mat", "userdef");

168 |CHAPTER 1: RELEASE NOTESELECTROCHEMISTRY MODULES CHANGES

There are changes for the Tertiary Current Distribution, Nernst-Planck interface. The
Java® API syntax for creating and accessing vectors and tensors has changed, as well as
the syntax for setting physics properties. See the following examples:• Specifying the diffusion tensor.
Old syntax:
model.physics("tcdee").feature("ice1").set("D_0", newString[]{"D1", "0", "0", "0", "D1", "0", "0", "0", "D1"});model.physics("tcdee").feature("ice1").set("D_1", newString[]{"D2", "0", "0", "0", "D2", "0", "0", "0", "D2"});model.physics("tcdee").feature("ice1").set("D_2", newString[]{"D3", "0", "0", "0", "D3", "0", "0", "0", "D3"});New syntax (includes the species name in the first argument of the set method):model.physics("tcdee").feature("ice1").set("D_c1", newString[]{"D1", "0", "0", "0", "D1", "0", "0", "0", "D1"});model.physics("tcdee").feature("ice1").set("D_c2", newString[]{"D2", "0", "0", "0", "D2", "0", "0", "0", "D2"});model.physics("tcdee").feature("ice1").set("D_c3", newString[]{"D3", "0", "0", "0", "D3", "0", "0", "0", "D3"});• Accessing tensor components (in the definitions of other variables, for example).
Old syntax:
Dxx_c1, Dxy_c1, Dxz_c1...

New syntax (component index after the species name):
D_c1xx, D_c1xy, D_c1xz...

• Specifying the reaction rate vector.
Old syntax:
model.physics("tcdee").feature("reac1").set("R_0", newString[]{"R1"});model.physics("tcdee").feature("reac1").set("R_1", newString[]{"R2"});model.physics("tcdee").feature("reac1").set("R_2", newString[]{"R3"});New syntax (includes the species name in the first argument of the set method):model.physics("tcdee").feature("reac1").set("R_c1", newString[]{"R1"});model.physics("tcdee").feature("reac1").set("R_c2", newString[]{"R2"});model.physics("tcdee").feature("reac1").set("R_c3", newString[]{"R3"});

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• Accessing vector components.
Old syntax:
tfluxx_c1, tfluxy_c1, tfluxz_c1

New syntax (component index after the species name):
tflux_c1x, tflux_c1y, tflux_c1z• Specifying initial values.
Old syntax:
model.physics("tcdee").feature("init1").setIndex("c2", "c20", 0);model.physics("tcdee").feature("init1").setIndex("c3", "c30", 0);model.physics("tcdee").feature("init1").setIndex("V", "V0", 0);

New syntax:
model.physics("tcdee").feature("init1").setIndex("initc", "c20",
1);model.physics("tcdee").feature("init1").setIndex("initc", "c30",
2);model.physics("tcdee").feature("init1").setIndex("initphil","V0");• Selecting properties.
Old syntax:
model.physics("tcdee").prop("Convection").set("Convection", 1,"0");model.physics("tcdee").prop("ConvectiveTerm").setIndex("Convectiv
eTerm", "noncons", 0);

New syntax (the property name corresponds to the section in the user interface):model.physics("tcdee").prop("TransportMechanism").
set("Convection", 1, "0");model.physics("tcdee").prop("AdvancedSettings").setIndex("Convect
iveTerm", "noncons", 0);

For information about API backward compatibility for the Surface Reactions interface,see the Chemical Reaction Engineering Module release notes.
ECAD IMPORT MODULE CHANGES• The default value for the grouping property of the Import function is now set tolayer. Previously, the default was all.
• For ODB++® and ODB++(X) files (the type property is odb), new rules apply forthe initialization of the importlayer property of the Import function. Now, only

170 |CHAPTER 1: RELEASE NOTESlayers of the types Metal and Dielectric are initialized with the string on in theimportlayer string array. Previously this also included layers of type Drill.
LIVELINK™ FOR SOLID EDGE®

CHANGESThe default value for the keepfree property of the LiveLinkSolidEdge function is
now set to on. Previously, the default was set to off.
LIVELINK™ FOR SOLIDWORKS®

CHANGESThe default value for the keepfree property of the LiveLinkSOLIDWORKS function is
now set to on. Previously, the default was set to off.

COMSOL 5.0 API Changes
DOCUMENTATIONThe COMSOL Multiphysics Programming Reference Manual replaces the
COMSOL API for Use with Java ® Reference Manual.
DEPRECATED METHODS

The following methods were deprecated in COMSOL 5.0:
TABLE 1-3: DEPRECATED METHODS AND THEIR REPLACEMENTS
DEPRECATED METHODNEW METHOD

com.comsol.model.OptFeature.field()

OptFeature.comp()

com.comsol.model.OptFeature.field(String)

OptFeature.comp(String)com.comsol.model.Group.identifier()

Group.paramName()com.comsol.model.Material.identifier()

ModelEntity.tag()com.comsol.model.MaterialModel.
identifier()

ModelEntity.tag()com.comsol.model.ModelNode.identifier()

ModelEntity.tag()com.comsol.model.physics.Physics.
identifier()

Use tag() instead.

com.comsol.model.physics.
MultiphysicsCoupling.identifier()

ModelEntity.tag()com.comsol.model.Group.identifier(String)Group.paramName(String)com.comsol.model.Material.
identifier(String)

ModelEntity.tag(String)com.comsol.model.MaterialModel.
identifier(String)

ModelEntity.tag(String)

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TABLE 1-3: DEPRECATED METHODS AND THEIR REPLACEMENTS

172 |DEPRECATED METHODNEW METHOD

com.comsol.model.ModelNode.
identifier(String)

ModelEntity.tag(String)com.comsol.model.physics.Physics.
identifier(String)

Use tag(string) instead.

com.comsol.model.physics.
MultiphysicsCoupling.identifier(String)

ModelEntity.tag(String)com.comsol.model.ModelEntity.name()

ModelEntity.label()com.comsol.model.ModelEntity.name(String)

ModelEntity.
label(String)com.comsol.model.ParameterEntity.
set(String, int, double)

Use the 0-based version(setIndex) instead.

com.comsol.model.ParameterEntity.
set(String, int, double)

Use the 0-based version(setIndex) instead.

com.comsol.model.ParameterEntity.
set(String, int, double[])Use the 0-based version(setIndex) instead.

com.comsol.model.ParameterEntity.
set(String, int, int)

Use the 0-based version(setIndex) instead.

com.comsol.model.ParameterEntity.
set(String, int, int[])

Use the 0-based version(setIndex) instead.

com.comsol.model.ParameterEntity.
set(String, int, int, double)

Use the 0-based version(setIndex) instead.

com.comsol.model.ParameterEntity.
set(String, int, int, int)

Use the 0-based version(setIndex) instead.

com.comsol.model.ParameterEntity.
set(String, int, int, String)

Use the 0-based version(setIndex) instead.

com.comsol.model.ParameterEntity.
set(String, int, String)

Use the 0-based version(setIndex) instead.

com.comsol.model.ParameterEntity.
set(String, int, String[]

Use the 0-based version(setIndex) instead.

CHAPTER 1: RELEASE NOTESCOMSOL 4.4 API Changes
PHYSICS INTERFACES• The default Initial Value features in the following interfaces have been extended:- Transport of Concentrated Species- Reacting Flow in Porous Media (rfcs)- Reacting Flow
- Rotating Machinery, Reacting Flow
Previously, only the initial mass fractions could be specified. Now, the initial values
can be specified in terms of mass fractions, mole fractions, molar concentrations,
number densities, or densities. When opening an old Model MPH file, Mixture
specification is set to Mass fractions, and the mass fractions specified are entered in
the respective text fields. In old model files for Java®, commands specifying theinitial value of a mass fraction return an error in version 5.0 and later. To specify the
initial mass fraction of a species w2, which is the second in the list of species (seen in
the Dependent Variables section when clicking the interface), change the COMSOLAPI Java® commandmodel.physics("chcs").feature("init1").set("w2", 1, "0.1");

tomodel.physics("chcs").feature("init1").set("w0", 2, "0.1");• The Pressure Acoustics, Frequency Domain interface and the Boundary Mode
Acoustics interface have a new default feature. If the default feature has been edited
in a Java® file, the following line should be added to the Java® file to obtain the oldbehavior for Pressure Acoustics, Frequency Domain:model.physics("acpr").feature().create("pam1","PressureAcousticsModel").selection().all();ormodel.physics("acbm").feature().create("pam1","PressureAcousticsModel").selection().all();for Boundary Mode Acoustics.
This line should be added directly after the line where the physics interface iscreated.

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• For models using mechanical contact, the variable field name in the solver settings
for the old contact variables is different than in earlier versions. For example:- In version 5.2 and later: mod1_solid_contact_old_p1,
mod1_solid_cm_old_p1.
- In version earlier than 5.0: mod1_solid_contact_p1_old,
mod1_solid_cm_p1_old.
• The parameter form in the property EquationForm can no longer be set to
ModeAnalysis in 3D and 2D axisymmetric calculations for the Pressure Acoustics,
Frequency Domain and Pressure Acoustics, Transient interfaces. In these cases, theparameter modeFreq has been removed.

COMSOL 4.3b API Changes
PHYSICS INTERFACES• The Crosswind diffusion formulation has been updated for all physics interfaces
supporting Crosswind diffusion. Models solved with the new formulation can givedifferent results than models solved in versions earlier than 4.3b. Java® files can be
modified to retain old crosswind formulations. Please contact COMSOL Support
for details.
• The default settings have changed for the Background Pressure Field in the Pressure
Acoustics interfaces. Add the following line to obtain the old behavior of thisfeature:model.physics("acpr").feature("bpf1").set("c", 1, "acpr.c_c");• In the Acoustics Module, the Far-Field Calculation feature is no longer available in
1D and 1D axisymmetric models.
• The shape function property border has been deprecated and replaced by order.

COMSOL 4.3a API Changes
GENERAL API CHANGES• Class files compiled with COMSOL Multiphysics version 4.3 or earlier need to berecompiled if they contain code that changes the contents of model.selection().
• The solutionintitle property governs whether to show solution information inplot titles. But since solution information has never been shown for 1D plots,

174 |CHAPTER 1: RELEASE NOTES

regardless of the content of the property, the property has been removed from 1D
plot groups.
FLUID FLOW INTERFACES API• Fluid flow features in the CFD Module and Microfluidics Module that previously
created a scalar Lagrange multiplier field with default name model.un_lm now
create a vectorial Lagrange multiplier field with default name model.u_lm. The
default component names in 3D are model.u_lm, model.v_lm, and model.w_lm,
respectively. Java® files must be updated accordingly.
• Weak constraints for the Interior Wall feature are no longer available. Any references
to its weak constraint parameter (weakConstraints) or Lagrange multipliers must
be removed.
• The Automatic setting for the Pseudo time stepping property now sets the variable<phtag>.locCFL to the built-in variable CFLCMP, which in turn triggers a PID
regulator via the automatic solver suggestions. Here, <phtag> is the physics
interface tag. Java® files where pseudo time stepping is active and the local CFL
number is set to Automatic must be modified by adding the commandmodel.physics(<tag>).prop("PseudoTimeProperty").set("CFLNumbExpr", 1, "Manual");before calling a solver.

COMSOL 4.3 API Changes• In the Acoustics Module, the far-field variables pfar and Lp_far have new nameswith full scope. They are now referred to as acpr.ffc1.pfar and®
acpr.ffc1.Lp_far, respectively. Any model files for Java that use the old variablenames in expressions (such as expressions used for plotting or evaluation that
include such old variable names) require a manual update.
• The following methods
model.physics(<tag>).feature(<ftag>).params();model.physics(<tag>).prop(propname).params();

are deprecated and replaced by the methods
model.physics(<tag>).feature(<ftag>).param();model.physics(<tag>).prop(propname).param();

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COMSOL 4.2a API Changes• Class files compiled with COMSOL Multiphysics version 4.1 or earlier need to berecompiled.
• The Far Field feature in the Electromagnetic Waves interface has changed from being
a boundary feature with a boundary selection only, to a domain feature with adomain selection. It also has a subfeature — a boundary selection.
• The dependent variable associated with gauge fixing in the Magnetic Fields,
Magnetic and Electric Fields, Electromagnetic Waves, and TransientElectromagnetic Waves interfaces is now unique to each interface. It is no longer
available in the model scope, for example, mod1.psi. Instead, the gauge fixing field
is only available in the interface scope, for example, as mod1.mf.psi.
• In the scattered field formulation in the Electromagnetic Waves interface, thescattered field is no longer available in the model scope (for example, mod1.relEx).
Instead, the scattered field is only available in the interface scope as, for example,
mod1.emw.relEx.
• In the Solid Mechanics interfaces (SolidMechanics, PiezoelectricDevices,
AcousticStructure, Poroelasticity, ThermallyInducedStresses,
JouleHeatingThermalExpansion, TransientAcousticStructure, andFluidStructureInteraction), tensors in local coordinate systems (el, eel, Sl,si, and ei) have new names. The coordinates of the local system (for example, x1,
x2, and x3) are no longer used. Instead 1, 2, and 3 are used together with double
indexing for all components. As an example, elX2 is replaced by el22 and elx2x3
is replaced by el23. The tensors si and ei are now called Sil and eil.
• In the Darcy’s Law interface and the Richards’ Equation interface in the Subsurface
Flow Module, fluid compressibility is now a material parameter and no longer has adefault value. If the default value was used, you now have to set the value. The
following example sets the permeability to the old default value:model.physics("dl").feature("smm1").set(chif_mat,userdef);model.physics("dl").feature("smm1").set(kappa,4e-10);• In the Poroelasticity interface in the Subsurface Flow Module, the fluid
compressibility and the Biot-Willis coefficient are now material parameters and nolonger have default values. If the default values were used, you now have to set thevalue. The following example sets the permeability to the old default value:model.physics("dl").feature("smm1").set(chif_mat,userdef);model.physics("dl").feature("smm1").set(kappa,4e-10);

176 |CHAPTER 1: RELEASE NOTES• The Level Set and Phase Field interfaces now include the Initial Interface feature by
default. If you have a model that was created in an earlier version of COMSOLMultiphysics, it will fail to create a feature with the same tag name.

COMSOL 4.1 API Changes
The following changes were made to the COMSOL API between versions 4.0a and
4.1:• In version 4.0a, the property nonlin in the stationary solver could have the valuesauto, on, off, and linearized. The default in most cases was auto, but in somecases, specifically in a frequency-domain study, the default was linearized. In
version 4.1, the possible values are auto, on, off, and linper, with auto as default,
except in the Frequency Domain, Linearized study step where the default is linper.
The value linearized can still be set, but this is treated as auto. If the problem islinear and the linearization point is zero, auto should give the same solution as
linearized. For nonlinear problems where the linearization point is zero, thesolution given by auto might be slightly different, and probably more accurate,
while changing to off should give exactly the same solution as linearized. When
there is a nonzero linearization point, it is relevant to use the linper option. This
option works like linearized, except that source terms that contribute to thelinearized problem must be enclosed by the linper operator.
• In the Darcy’s Law interface, Brinkman interface, Richards’ Equation interface, andPoroelasticity interface (in the CFD Module and Subsurface Flow Module), thepermeability and porosity are now material parameters and no longer have default
values. If the default values were used in a model file for Java®, you now have to set
them. The following example sets the permeability to the old default value:model.physics("dl").feature("dlm1").set(kappa_mat,userdef);model.physics("dl").feature("dlm1").set(kappa,3e-11);• The pressure variable in solid mechanics, typically solid.pw, now only getsallocated degrees of freedom for incompressible materials. If you have referred to it,
for example, during segregation in the solver, the code will have to be changed toremove the field.
• The solution to eigenvalue and eigenfrequency problems may now appear in adifferent order.
• The Batteries & Fuel Cells Module’s boundary feature,
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means that files that explicitly refer to the old default tag name must be modified torefer to the new tag name.

COMSOL 4.0a Java API Changes
The following changes were made to the COMSOL API between versions 4.0 and
4.0a:• The units of the load face parameter (Fph) of the Phase feature in
AcousticStructure, TransientAcousticStructure,
ThermallyInducedStresses, SolidMechanics,
JouleHeatingThermalExpansion, Poroelasticity, andFluidStructureInteraction have changed from degrees to radians.
• The physics.field() operator for Beam and Truss are not backward compatible
with 4.0. Scalar fields are now vector fields.
• The variables for strain and stress in the Shell interface have been renamed. Variablenames that began with a lowercase s now begin with an uppercase S. For variables
names that ended in lowercase l (L), the letter was moved to the third position. For
example, emXXl is now emlXX.
• Force loads on solids and trusses have been moved from the material to the spatial
frame. This means that the index notation of some variables has changed fromuppercase XYZ to lowercase xyz.
• The acoustics interfaces (PressureAcoustics, TransientPressureAcoustics,
AcousticStructure, and TransientAcousticStructure) have been moved
from the material to the spatial frame. This means that the index notation of vector
variables has changed from uppercase XYZ to lowercase xyz.
This concludes the release notes for COMSOL Multiphysics version 5.4.

178 |CHAPTER 1: RELEASE NOTESI n d e x
A

AC/DC Module

new and updated models in 74

backward compatibility 37

new functionality in 72

new applications in 37

Electrodeposition Module

new functionality 36

new and updated models in 77

Acoustics Module
backward compatibility 42

new functionality in 75
F

new functionality in 40

Fatigue Module
backward compatibility 78

Application Builder, new functionality in

new functionality in 78

13
G
B

backward compatibility, general consid-

Geomechanics Module

erations 24

new functionality in 79

Battery & Fuel Cells Module

new models in 80

new functionality in 44
Cgeometry and mesh, new functionality

CAD Import Module
new functionality in 48

general new functionality 13

for 18H

CFD Module

Heat Transfer Module
backward compatibility 89, 91, 93–94

backward compatibility 54–55

new applications in 87

new functionality in 53

new functionality in 81

new models in 54
Chemical Reaction Engineering ModuleLbackward compatibility 165

backward compatibility 64
new functionality in 62

new functionality in 164

COMSOL API changes 166

LiveLink™ products for CAD
new functionality in 48

COMSOL Multiphysics, new functionality in 15
COMSOL Server, new functionality in 15
Corrosion Module
backward compatibility 70
new and updated models in 69
new functionality 68
D

LiveLink for MATLAB

Design Module
new functionality in 48

M

Material Library
new and updated material data in 163
new material data in 163
MEMS Module
backward compatibility 108
new functionality in 103
Microfluidics Module
backward compatibility 109
new functionality in 109

E

ECAD Import Module
backward compatibility 71

Mixer Module
new functionality in 111

Electrochemistry Module

I N D E X | 179

Molecular Flow Module
backward compatibility 112
Multibody Dynamics Module
new functionality in 113
N

Nonlinear Structural Materials Module
new functionality in 115
new models in 116

new functionality in 149
new models in 154
studies and solvers, new functionality in
19

Subsurface Flow Module
backward compatibility 158
new functionality in 157
new models in 158

O

operators, functions, and definitions,
new and updated 19
Optimization Module
new functionality in 118

P

Particle Tracing Module
backward compatibility 120
new applications in 120
new functionality in 120
Pipe Flow Module
backward compatibility 124
Plasma Module
backward compatibility 126

R

Ray Optics Module
backward compatibility 131
new applications in 131
new functionality in 129
results and visualization, new functionality in 22
RF Module
new and updated apps and models in
138

new functionality in 136
Rotordynamics Module
new functionality in 141
new models in 142
S

Semiconductor Module
new applications in 147
new functionality in 144
Structural Mechanics Module
backward compatibility 155

180 | I N D E X

W Wave Optics Module

new functionality in 159
new models in 162