NASA/CR—2015–218481 

 

11 Foot Unitary Plan Tunnel Facility Optical 

Improvement Large Window Analysis 

Veronica M. Hawke 

Science and Technology Corporation, Hampton, VA 

Ames Research Center, Moffett Field, California

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February 2015
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NASA/CR—2015–218481 

 

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11 Foot Unitary Plan Tunnel Facility Optical 

Improvement Large Window Analysis 

Veronica M. Hawke 

Science and Technology Corporation, Hampton, VA 

Ames Research Center, Moffett Field, California 

National Aeronautics and 

Space Administration

Ames Research Center 

Moffett Field, CA 94035-1000 

February 2015
Acknowledgments 

 This work is being done for the AA office at NASA Ames and at the request of the 

Unitary Plan Tunnel group under the direction of John Melton. The author greatly appreciates 

the help given by Tom Pulliam, William Chan, Henry Lee, John Melton and Michael Aftosmis in 

obtaining and preparing the CRM (see section 2.1 below) geometry for use in this study. 

 The NAS user services group was very helpful in getting the cases to run efficiently on 

the NAS computers despite numerous issues with the machines themselves.

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Hanover, MD 21076-1320 

443-757-5802 
i 

Table of Contents 

Acronyms/Abbreviations ...................................................................................................................................iii

1.0 Overview ....................................................................................................................................................... 1

2.0 Geometry....................................................................................................................................................... 1

2.1 CRM Modeling ......................................................................................................................................... 3

3.0 Computational Analysis ................................................................................................................................ 3

3.1 Results for Large Windows with Extra Slots, Tail Model (Set 1) ............................................................ 9

3.2 Results for Large Window with Extra Slots, CRM Model (Set 2) ......................................................... 12

3.3 Results for Large Windows without Extra Slots, CRM Model (Set 3) .................................................. 15

4.0 Conclusions/Future Work ........................................................................................................................... 19

5.0 References ................................................................................................................................................... 20

 
ii

Table of Figures 

Figure 1 Full Original Geometry ........................................................................................................................ 1

Figure 2 Original Test Section ............................................................................................................................ 2

Figure 3 Open Floor Test Section ....................................................................................................................... 2

Figure 4 Closed Floor Test Section .................................................................................................................... 2

Figure 5 Large Window with Extra Slots ........................................................................................................... 2

Figure 6 Large Window without Extra Slots ...................................................................................................... 2

Figure 7 Tail Installed in Test Section ................................................................................................................ 3

Figure 8 CRM Installed in Test Section ............................................................................................................. 3

Figure 9 Floor Open, Original Windows/Tunnel, wsrun4, Sets 1, 2 and 3 ........................................................ 5

Figure 10 Floor Closed, Original Windows/Tunnel, wsrun7, Sets 1, 2 and 3 .................................................... 5

Figure 11 Floor Closed, Large Windows, Extra Slots, wsrun21, Sets 1 and 2 .................................................. 5

Figure 12 Floor Closed, Original Windows/Tunnel, Tail in Test Section, wsrun29, Set 1 ................................ 6

Figure 13 Floor Closed, Large Windows, Extra Slots, Tail in Test Section, wsrun30, Set 1 ............................. 6

Figure 14 Floor Closed, Original Windows/Tunnel, CRM in Test Section, wsrun37, Set 2 ............................. 6

Figure 15 Floor Closed, Large Windows, Extra Slots, CRM in Test Section, wsrun38, Set 2 .......................... 7

Figure 16 Floor Closed, Original Window/Tunnel, CRM in Test Section at 4 deg., wsrun39, Sets 2 and 3 ..... 7

Figure 17 Floor Closed, Large Windows, Extra Slots, CRM in Test Section at 4 deg., wsrun40, Set 2............ 7

Figure 18 Floor Closed, Large Windows, No Extra Slots, CRM in Test Section, wsrun46, Set 3 .................... 8

Figure 19 Floor Closed, Large Windows, No Extra Slots, CRM in Test Section at 4 deg., wsrun49, Set 3 ...... 8

Figure 20 Floor Closed, Original Windows/Tunnel, CRM in Test Section wsrun51, Set 3 .............................. 8

Figure 21 Floor Closed, Large Windows, No Extra Slots, wsrun53, Set 3 ........................................................ 9

Figure 22 Large Window with Extra Slots Close-Up ....................................................................................... 10

Figure 23 Mach along Tunnel Centerline Cart3D Results for Set 1 ................................................................. 10

Figure 24 Pressure Tap Lines in Test Section .................................................................................................. 11

Figure 25 Set 1 Left Floor (Line4) Mach vs. Tunnel Station ........................................................................... 11

Figure 26 Set 1 Right/South Wall Upper (Line 7) Mach vs. Tunnel Station.................................................... 12

Figure 27 Mach along Tunnel Centerline Cart3D Results for Set 2 ................................................................. 13

Figure 28 Set 2 Left Floor (Line 4) Mach vs. Tunnel Station .......................................................................... 13

Figure 29 Set 2 Right/South Wall Upper (Line 7) Mach vs. Tunnel Station.................................................... 14

Figure 30 Set 2 Mach Distribution at Root Section of CRM ............................................................................ 14

Figure 31 Set 2 Mach Distribution at Mid-span Section of CRM .................................................................... 15

Figure 32 Set 2 Mach Distribution at Tip Section of CRM .............................................................................. 15

Figure 33 Large Window without Extra Slots Close Up .................................................................................. 16

Figure 34 Mach along Tunnel Centerline Cart3D Results for Set 3 ................................................................. 16

Figure 35 Set 3 Left Floor (Line 4) Mach vs. Tunnel Station .......................................................................... 17

Figure 36 Set 3 Right/South Wall Upper (Line 7) Mach vs. Tunnel Station.................................................... 17

Figure 37 Set 3 Mach Distribution at Root Section of CRM ............................................................................ 18

Figure 38 Set 3 Mach Distribution at Mid-span Section of CRM .................................................................... 18

Figure 39 Set 3 Mach Distribution at Tip Section of CRM .............................................................................. 18

Table of Tables 

Table 1 Cart3D Cases Run for Large Window Study......................................................................................... 4
iii

Acronyms/Abbreviations 

AIAA : American Institute of Aeronautics and Astronautics 

CAD : Computer Aided Drafting/Design 

Cart3D : Cartesian 3 Dimensional 

CRM : Common Reference Model 

DPW : Drag Prediction Workshop 

ITAR : International Traffic in Arms Regulations 

STAR-CCM+ : Simulation of Turbulence in Arbitrary RegionsComputational Continuum Mechanics 

TS : Tunnel Station, all values given are in inches 

UPWT : Unitary Plan Wind Tunnel 
1

1.0 Overview 

 The test section of the 11 by 11-foot Unitary Plan Transonic Wind Tunnel (11-foot 

UPWT) may receive an upgrade of larger optical windows on both the North and South sides. 

These new larger windows will provide better access for optical imaging of test article flow 

phenomena including surface and off body flow characteristics. The installation of these new 

larger windows will likely produce a change to the aerodynamic characteristics of the flow in the 

Test Section. In an effort understand the effect of this change, a computational model was 

employed to predict the flows through the slotted walls, in the test section and around the model 

before and after the tunnel modification. This report documents the solid CAD model that was 

created and the inviscid computational analysis that was completed as a preliminary estimate of 

the effect of the changes. 

2.0 Geometry 

 The solid CAD geometry baseline used for this study is documented in Reference (1) and 

a cut-away view is shown in Figure 1. It is a full CAD model of the 11-foot UPWT from the 

forward nozzle/inlet diffuser to the end of the aft diffuser for use with computational fluids 

codes. An image of the original tunnel test section is shown in Figure 2. In preparation for the 

half body model installations the floor of the tunnel was closed as shown in Figure 3 (open) and 

Figure 4 (closed). The test section was also modified to represent the intended study geometry 

by closing off two rows of slots and baffles with a large window plate feature. Two versions 

were analyzed, one with an extra row of slots next to the upper and lower slots and one without, 

as shown in 

Figure 5 and 

Figure 6 respectively. Two different representative half-body models were used in this study. 

Due to time constraints, the first model chosen was a readily available simplified (non-ITAR) 

version of the Boeing 757 tail described in Reference (2) and shown installed in Figure 7. The 

Common Reference Model (CRM) shown in Figure 8 was used for the latter portion of the study 

and its implementation is described in Section 2.1 below. 

Figure 1 Full Original Geometry 
2

Figure 2 Original Test Section 

Figure 3 Open Floor Test Section Figure 4 Closed Floor Test Section

Figure 5 Large Window with Extra Slots Figure 6 Large Window without Extra Slots 
3

Figure 7 Tail Installed in Test Section Figure 8 CRM Installed in Test Section

2.1 CRM Modeling 

 The wing body sample model chosen for this study was the AIAA CRM (Common 

Research Model) used for Drag Prediction Workshop 5 (DWP5).The geometry was obtained in a 

triangulated format and not as solid CAD geometry. It was scaled and located to meet the needs 

of this study. Figure 8 shows the CRM installed in the computational model. Details of how the 

CRM was integrated into the model follow. 

 First, the half model of the CRM wing and body was created from the original overset 

triangulated grids. Two versions, coarse and refined were produced. In the end the coarse mesh 

was deemed adequate for the window study purposes and so was used for the remainder of the 

process. STAR-CCM+ was used to close the mesh along the vehicle centerline symmetry plane 

to create a water tight geometry. The model was then opened in Overgrid and scaled, translated, 

and rotated to the correct location for use in the 11-foot UPWT CAD model. A 1” high standoff 

skirt at the CRM symmetry plane was added in STAR-CCM+. Attempts were then made to 

union the CRM model with the 11 foot tunnel geometry mesh using Cart3D tools. While it was 

possible to union it with a large flat plate that represented the tunnel floor, it was not readily 

possible to incorporate the resulting geometry back into the full tunnel geometry using tools such 

as MatLab in the same way the strut is merged with the full model. STAR-CCM+ was used to 

do the final union of the CRM model with the full tunnel and output the combined triangulation. 

3.0 Computational Analysis 

 To get an initial check of the effect of the large windows, Cart3D (3) analysis was conducted on 

various configurations. Three sets of results were delivered. The first included a tail model (referenced 

above), the second consisted of the CRM geometry in the test section with an extra set of slots included above 

and below the large windows, and the third was with CRM installed and the extra slots removed. 
4

Table 1 gives configuration and other information for the cases delivered. The first set studied 

had the strut centerbody positioned at a z-offset of zero. All subsequent studies with the CRM 

model installed had the centerbody z-offset at +38 inches to replicate the usual position for half 

body testing in the 11-foot UPWT. All cases were run with a target centerline Mach number of 

0.85 to represent the highest expected Mach number for this type of geometry. The geometry 

was selected as representative of the larger (highest blockage) type of model that would most 

likely be affected by changes in the wall porosity and flow. All cases averaged around 32 – 33 

million grid cells for the solution and contained about 2.1 – 2.3 million surface mesh elements to 

define the geometry. The cases listed in the table represent the best obtained solution for the 

given configuration in a given set. In all sixty-two Cart3D runs were made for this study. 

Results are shown for the tunnel centerline, along two lines of pressure ports in the test section, 

and on three sections of the wing for the CRM cases. Figure 9 through Figure 21show the 

surface Mach numbers for a left and right isometric view for each of the configurations. 

Table 1 Cart3D Cases Run for Large Window Study 

Case 

Name Set 

Floor 

Closed 

Large 

Window 

Extra 

Baffles 

Model 

in Test 

Section 

Nose 

Angle of 

Model 

(deg.) 

Centerbody 

Z offset (in) 

Average 

Reference 

Mach 

wsrun4 1,2,3 no no - no - 0 0.849 

wsrun7 1,2,3 yes no - no - 0 0.846 

wsrun21 1,2 no yes yes no - 0 0.853 

wsrun29 1 yes no - tail 0 0 0.857 

wsrun30 1 yes yes yes tail 0 0 0.859 

wsrun37 2 yes no - CRM 0 38 0.867 

wsrun38 2 yes yes yes CRM 0 38 0.872 

wsrun39 2,3 yes no - CRM 4 38 0.847 

wsrun40 2 yes yes yes CRM 4 38 0.860 

wsrun46 3 yes yes no CRM 0 38 0.854 

wsrun49 3 yes yes no CRM 4 38 0.851 

wsrun51 3 yes no - CRM 0 38 0.852 

wsrun53 3 yes yes no no - 38 0.853 
5

Figure 9 Floor Open, Original Windows/Tunnel, wsrun4, Sets 1, 2 and 3 

Figure 10 Floor Closed, Original Windows/Tunnel, wsrun7, Sets 1, 2 and 3 

Figure 11 Floor Closed, Large Windows, Extra Slots, wsrun21, Sets 1 and 2 
6

Figure 12 Floor Closed, Original Windows/Tunnel, Tail in Test Section, wsrun29, Set 1 

Figure 13 Floor Closed, Large Windows, Extra Slots, Tail in Test Section, wsrun30, Set 1 

Figure 14 Floor Closed, Original Windows/Tunnel, CRM in Test Section, wsrun37, Set 2 
7

Figure 15 Floor Closed, Large Windows, Extra Slots, CRM in Test Section, wsrun38, Set 2 

Figure 16 Floor Closed, Original Window/Tunnel, CRM in Test Section at 4 deg., wsrun39, Sets 2 and 3 

Figure 17 Floor Closed, Large Windows, Extra Slots, CRM in Test Section at 4 deg., wsrun40, Set 2 
8

Figure 18 Floor Closed, Large Windows, No Extra Slots, CRM in Test Section, wsrun46, Set 3 

Figure 19 Floor Closed, Large Windows, No Extra Slots, CRM in Test Section at 4 deg., wsrun49, Set 3 

Figure 20 Floor Closed, Original Windows/Tunnel, CRM in Test Section wsrun51, Set 3 
9

Figure 21 Floor Closed, Large Windows, No Extra Slots, wsrun53, Set 3 

3.1 Results for Large Windows with Extra Slots, Tail Model (Set 1) 

 The first set of results were presented to the wind tunnel group on July 28, 2014. Five 

configurations were shown to provide a first check of the effects of a large window installation in 

the 11-foot UPWT. The model used was the Boeing 757 simplified tail scaled down to fit in the 

tunnel. The tail span was 7.6 feet including the blister. The forward-most tunnel station of the 

blister/tail was about 55.5 inches and the aft-most was approximately 189.5 inches. The cases 

with the tail installed were all run at a nominal nose rotation of zero degrees. All of the large 

window cases for this set included the extra slots both above and below the windows. See Figure 

22 for a close-up view of the additional slots on the right (South) window. The large window is 

installed between tunnel stations 99 and 231 combining the current middle three panel sets. The 

target Mach number was measured along the primary test section centerline without the model 

installed and was measured at the forward portion of the tunnel when the model was installed. 

Figure 23 shows the tunnel centerline Mach number distribution extracted from the Cart3D 

simulation. Shown also are notional representations of the tunnel window and the extent of the 

model along the tunnel centerline. 
10

Figure 22 Large Window with Extra Slots Close-Up 

Figure 23 Mach along Tunnel Centerline Cart3D Results for Set 1 

 Figure 24 shows the positions of the test section pressure tap lines. Pressure data for 

tunnel tests is collected along these lines. Solution data is also collected from Cart3D along 

these lines. Figure 25 and Figure 26 show the local surface Mach number along lines 7 (above 

the right/South wall window) and 4 (to the left of the model on the floor), respectively 

(highlighted in blue in Figure 24). 
11

Figure 24 Pressure Tap Lines in Test Section 

Figure 25 Set 1 Left Floor (Line4) Mach vs. Tunnel Station 
12

Figure 26 Set 1 Right/South Wall Upper (Line 7) Mach vs. Tunnel Station 

3.2 Results for Large Window with Extra Slots, CRM Model (Set 2) 

 The second set of results with the CRM installed in the test section and showing the 

effects of a large window with extra sets of slots were delivered to the wind tunnel group via an 

Excel spreadsheet and PowerPoint slide presentation. The CRM wing half-span was 7.3 feet 

including the half body. The forward-most tunnel station of the body was about 12.5 inches and 

the aft-most point was approximately 198.5 inches. The cases with the CRM installed were run 

at nominal nose rotations of zero degrees and at 4 degrees (nose up/tunnel right). All of the large 

window cases for this set included the extra slots both above and below the window. The target 

Mach number was measured along the primary test section centerline without the model installed 

and was measured at the forward portion of the tunnel when the model was installed. Figure 27 

shows the tunnel centerline Mach number distribution extracted from the Cart3D simulation. 

Shown also are notional representations of the tunnel window and the extent of the model along 

the tunnel centerline Figure 28 and Figure 29 show the local surface Mach number along tunnel 

pressure tap lines 7 (above the right/South wall window) and 4 (to the left of the model on the 

floor), respectively (see Figure 24). 
13

Figure 27 Mach along Tunnel Centerline Cart3D Results for Set 2 

Figure 28 Set 2 Left Floor (Line 4) Mach vs. Tunnel Station 
14

Figure 29 Set 2 Right/South Wall Upper (Line 7) Mach vs. Tunnel Station 

 Three sections of the CRM wing were compared with and without the large windows 

(w/extra slots), with the CRM at 0 and 4 degrees. Figure 30 shows the Mach surface values vs. 

tunnel station for a wing section (both left/bottom and right/upper surface) near the root. Figure 

31 and Figure 32 show the Mach values for a mid-span section and a section near the tip, 

respectively. 

Figure 30 Set 2 Mach Distribution at Root Section of CRM 
15

Figure 31 Set 2 Mach Distribution at Mid-span Section of CRM 

Figure 32 Set 2 Mach Distribution at Tip Section of CRM 

3.3 Results for Large Windows without Extra Slots, CRM Model (Set 3) 

 The third set is similar to the second, using the same wing body model (CRM) in the 

same positions (0° and 4°), but it does not include the added set of slots along the top and bottom 

of the windows. A close-up view is shown in Figure 33. This configuration was requested as it 

more likely reflects the initial test configuration (where the current slots will be taped over in the 

region of the large windows). Figure 34 shows the predicted Mach distribution along the 

centerline of the tunnel for set 3. Similar to set 2, Figure 35 and Figure 36 show the local surface 

Mach number along tunnel pressure tap lines 7 (above the right/South wall window) and 4 (to the 

left of the model on the floor), respectively (see Figure 24) for set 3. 
16

Figure 33 Large Window without Extra Slots Close Up 

Figure 34 Mach along Tunnel Centerline Cart3D Results for Set 3 
17

Figure 35 Set 3 Left Floor (Line 4) Mach vs. Tunnel Station 

Figure 36 Set 3 Right/South Wall Upper (Line 7) Mach vs. Tunnel Station 

 Again as with set 2 three sections of the CRM wing were compared with and without the 

large windows (w/o extra slots), with the CRM at 0 and 4 degrees. Figure 37 shows the Mach 

surface values vs. tunnel station for a wing section (both left/bottom and right/upper surface) 

near the root. Figure 38 and Figure 39 show the Mach values for a mid-span section and a 

section near the tip, respectively. 
18

Figure 37 Set 3 Mach Distribution at Root Section of CRM 

Figure 38 Set 3 Mach Distribution at Mid-span Section of CRM 

Figure 39 Set 3 Mach Distribution at Tip Section of CRM 
19

4.0 Conclusions/Future Work 

 On the whole, the results seen from Cart3D followed the expected pattern with the shocks 

occurring further aft with the large windows installed. The overall shape and characteristics of 

the solution with and without the large windows seem similar. The sensitivity at the CRM wing 

tip with and without the extra slots on the large windows could be explored further by checking 

nearby sections. The choice of tip section may be too close to rapidly changing tip effects and 

would be better represented by a cut slightly further inboard. Additional simulations at lower 

Mach numbers closer to those used by other large transports may be useful. Further work can be 

done to extract Cp values on the wing in order to compare with current data on the CRM. 
20

5.0 References 

1. Hawke, V. 11-by 11-Foot Transonic Leg of the Unitary Plan Wind Tunnel (UPWT) CAD 

Model. 2014. NASA/CR--2014--218371. 

2.. Active Flow Control Vertical Tail CAD Model for Computational Fluid Dynamics Analysis. 

2014. NASA/CR--2014--218355. 

3. Aftosmis, M. Cart3D Main Page. [Online] [Cited: 8 27, 2014.] 

http://people.nas.nasa.gov/~aftosmis/cart3d/.