bluuebunny/crossref_metadata_2025_split huggingface dataset:
A phenomenological constitutive model for magnetostrictive materials and ferroelectric ceramics
Authors: Klinkel Sven , Linnemann Konrad 
Published: February 2009

AbstractThe contribution is concerned with a thermodynamic consistent constitutive model for magnetostrictive materials and ferroelectric ceramics. It captures the nonlinear phenomenological behavior which is described by hysteresis effects. Magnetostrictive alloys and ferroelectric ceramics belong to the multifunctional materials. In recent years these materials have become widely–used in actor and sensor applications. They characterize an inherent coupling between deformation and magnetic or electric field. Due to the similarities of the coupled differential equations a uniform approach is applied for both phenomena. The presented three–dimensional material model is thermodynamically motivated. It is based on the definition of a specific free energy function and a switching criterion. Furthermore an additive split of strain and the magnetic or electric field in a reversible and an irreversible part is suggested. The irreversible quantities serve as internal variables, which is analog to plasticity theory. A one–to–one–relation between the two internal variables provides conservation of volume for the irreversible strains. The presented material model can approximate the ferromagnetic or ferroelectric hysteresis curve and the related butterfly hysteresis. Furthermore an extended approach for ferrimagnetic behavior, which occurs in magnetostrictive materials, is presented. Some numerical simulations demonstrate the capability of the presented model. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermomechanical modeling and simulation of aluminum alloys during extrusion process
Authors: Parvizian Farhad , Kayser Tobias , Hortig Christian , Svendsen Bob 
Published: February 2009

AbstractThe purpose of this work is to simulate the microstructure development of aluminum alloys during hot metal forming processes such as extrusion with the help of the Finite Element Method (FEM). To model the thermomechanical coupled behavior of the material during the extrusion process an appropriate material model is required. In the current work a Johnson–Cook like thermoelastic viscoplastic material model is used. To overcome the numerical difficulties during simulation of extrusion such as contact problem and element distortion an adaptive meshing system is developed and applied. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Asynchronous method for the coupled simulation of mechatronic systems
Authors: Petridis Kosmas , Klein Andreas , Beitelschmidt Michael 
Published: February 2009

AbstractA new method for coupled simulation of mechatronic systems based on a comparison of the actual time step of the simulation tools and the utilization of inter– and extrapolation methods will be presented in this contribution. Since the method does not use constant synchronization time points, the problem of setting the appropriate macro step size is avoided. The example of a drill driver model is used to compare the results of the proposed method with those obtained by a conventional approach. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Implementation of a Free‐locking Composite Piezoelectric Shell Element
Authors: Lammering Rolf , Yang Fan 
Published: February 2009

AbstractIn this contribution, a free–locking shell element with piezoelectric ceramic layers is presented. The material law and the constitutive equations of the coupled electro–mechanical problem are derived in convective coordinates, so that the presented element accounts for geometrical nonlinearities [2]. To avoid zero–energy mode and locking effects of the thin shell structure, assumed natural strain (ANS) method [1] is implemented. Finally, some numerical examples demonstrate the ability of this element to solve linear and nonlinear problems. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Homogenization of Linear Elastic Properties of Silicon Nitride
Authors: Böhlke Thomas , Jöchen Katja , Langhoff Tom‐Alexander 
Published: February 2009

AbstractThe effective linear elastic properties of silicon nitride (Si3N4) are estimated based on first–, third–, and fifth–order bounds of the strain energy density. This specific type of material is a mixture of two linear elastic materials with different material symmetries. The β‐Si3N4 grains have a hexagonal symmetry with significant amount of anisotropy, whereas the glassy phase is approximately isotropic. The results are as follows: i) The fifth–order upper and lower bounds are almost identical. Therefore, these bounds are sufficient for estimating the effective elastic properties. ii) For fixed elastic constants of the hexagonal β‐Si3N4 grains, the effective properties of Si3N4 are determined as a function of properties of the glassy phase and its volume fraction. The corresponding diagrams allow for the inverse identification of the elastic properties of the glassy phase. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Finite element (FE) simulation of textile‐reinforced composites using a COSSERAT Element
Authors: Branke D. , Brummund J. , Haasemann G. , Ulbricht V. 
Published: February 2009

AbstractThe efficient simulation of textile reinforced composites requires reliable material parameters describing the macroscopic material behavior. Due to the micro–structure, decoupled tensile and bending stiffnesses are observed in experimental investigations. This motivates the use of higher order continuum theories. For numerical simulation of this material behavior, the formulation and application of a volume element based on the Cosserat continuum theory is presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigations on an elastic micropolar continuum model for large deformations
Authors: Jänicke R. , Sehlhorst H.‐G. , Steeb H. , Diebels S. , Düster A. , Rank E. 
Published: February 2009

AbstractThe mechanical behaviour of cellular materials is dominated by the influence of the microtopology. If the characteristic microstructural length scale becomes comparable to the macroscopical length scale, classical homogenisation strategies fail and have to be replaced by extended approaches. In the present contribution, we present a micropolar continuum model for large deformations introducing the microrotation as an additional degree of freedom. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On estimates for the effective shear modulus of cubic crystal aggregates
Authors: Jöchen Katja , Böhlke Thomas , Fritzen Felix 
Published: February 2009

AbstractTo avoid time–consuming computations, several analytical approaches can be used to estimate the elastic properties of polycrystalline aggregates. In this paper we compute some well–known bounds and estimates for the effective shear modulus of aggregates of cubic crystals and compare them with results from finite element simulations using a representative volume element (RVE). It is shown that among the evaluated approaches, the singular approximation results in the best agreement with the RVE simulations for the examined materials. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Multiscale Approach for the Modelling of Failure
Authors: Mergheim Julia 
Published: February 2009

AbstractIn the present contribution a multi–scale – or rather two–scale – framework for the modelling of propagating discontinuities is introduced. The method is based on the Variational Multiscale Method. The displacement field is additively decomposed into a coarse– and a fine–scale part. This kinematic assumption implies a separation of the weak form in two equations, corresponding to the coarse–scale and the fine–scale problem. Both scales are discretized by means of finite elements. On the fine–scale, due to a much finer discretization, a heteregeneous mesostructure and propagating mesocracks can be considered. The propagation of the mesocracks is simulated independently of the underlying finite element mesh by discontinuous elements. The performance of the multi–scale approach is shown by a numerical example. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation and Modeling the Mechanical Behavior of Textile Reinforced Composites by Combining the Binary Model and X‐FEM
Authors: Haasemann Georg , Kästner Markus , Prüger Stefan , Ulbricht Volker 
Published: February 2009

AbstractThis paper presents a new efficient modeling strategy based on the combination of Binary Model and X–FEM. It is applied to represent the inner architecture of textile reinforced composites where the fabric is characterized by a complex geometry. Homogenization methods are used to compute the effective elastic material properties. Thereby, the discrete formulation of periodic boundary conditions is adapted. Finally, the results in terms of effective material properties reveal a good agreement with parameters obtained by experimental tests. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Homogenization of transmission conditions for analysis of acoustic waves in domains with perforated barriers
Authors: Rohan Eduard , Lukeš Vladimír 
Published: February 2009

AbstractWe consider structures like the muffler of the engine exhaust, where the acoustic waves propagate through periodically perforated barriers. Recently we proposed a homogenized model [6] of the acoustic transmission through the layer with embedded rigid obstacles of arbitrary shapes, which represent the perforation. The homogenized model describes relationship between jump of the acoustic pressures p+ and p− at the discontinuity interface Γ0 and the transverse acoustic velocity g0±, on introducing in–layer acoustic pressure p0 which describes wave propagation along the interface. The coupling between the transversely and the tangential acoustic velocities may become important for certain types of perforations. A sensitivity study was done which reveals remarkable dependence of wave transmission losses on the geometry of the perforation. Examples of 3D perforation geometries were treated. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A two‐algebraic turbulence model for compressible flow in turbomachinery cascade
Authors: Dumitrache Alexandru , Dumitrescu Horia 
Published: February 2009

AbstractThe objective of this study is to examine the Baldwin–Lomax turbulence model in a finite volume solver to introduce a computer code for complex two–dimensional flows in turbomachinery. The turbulent model was tested with investigating the turbulent flow over a flat plate and other test cases. Three test cases are presented and the computed results are compared with experimental data. The calculated velocity profile agreed well with the experimental data in plate test case and the solver is validated in test case of flow over a semi NACA–0012 airfoil. The solver is used for flow through a multi–blade cascade of an axial compressor in design condition to show its capability of multi–block solution. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of the Reynolds‐stress and dissipation‐rate decay and anisotropy from DNS of grid‐generated turbulence
Authors: Özyilmaz N. , Beronov K. N. , Delgado A. 
Published: February 2009

AbstractGrid–generated turbulence is a classical but still controversial topic, one open issue being the spatial decay rate of turbulent energy. We study the influence of grid geometry on the Reynolds–stress and dissipation–rate tensors, including the range and exponent of their self–similar spatial decay. DNS using a validated lattice Boltzmann code at mean–flow Reynolds numbers up to 1400 are performed, comparing square grids with blockage ratios from 0.05 to 0.49. A clear picture of spatial distribution and self–similarity emerges for the statistics of interest: Axisymmetry is excellently confirmed. A consistent power law decay is found in the self–similar decay region beyond 10 grid stride lengths downstream. Its exponent of –5/3 can be obtained, for weak turbulence, from a spatial flux balance reminiscent of the constant transport through the inertial range of isotropic turbulence. In the near–grid region, on the other hand, differences in Reynolds stress components are pronounced while those between dissipation tensor components are only recognizable very close to the grid, where a strong dependence on grid porosity is found. A normalization with respect to porosity is proposed that collapses the data from all runs. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Similarity Reductions of a Generalized Double Dispersion Equation
Authors: Bruzón M. S. , Gandarias M. L. 
Published: February 2009

AbstractWe apply the Lie–group formalism to deduce symmetries of a generalized double dispersion equation. We derive the ordinary differential equation to which the equation is reduced. We obtain exact solutions which can be expressed by various single and combine nondegenerative Jacobi elliptic function solutions and their degenerative solutions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Lie algebra methods in turbulence
Authors: Grebenev V.N. , Oberlack M. , Grishkov A.N. 
Published: February 2009

AbstractApproximate Lie symmetries of the Navier–Stokes equations are used for the applications to scaling phenomenon arising in turbulence. We show how the scaling groups obtained can be used to introduce the Reynolds number dependence into scaling laws explicitly for stationary parallel turbulent shear flows. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Transparent boundary conditions as dissipative closures
Authors: Oliver Marcel , Bühler Oliver 
Published: February 2009

AbstractWe study the systematic development of subgrid closures via transparent boundary conditions in spectral space in one of the simplest possible settings: passive tracer transport in a doubly–periodic shear flow that has small support in the spectral domain. The resulting closure schemes have small dissipation rate errors and are only minimally over–dissipative for unsteady flows. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Interaction of the Filter and Spatial Discretisation Operators for Large‐Eddy Simulation Using the Approximate Deconvolution Model
Authors: Tomm S. , von Terzi D. A. , Fröhlich J. 
Published: February 2009

AbstractThe Approximate Deconvolution Model (ADM) for Large–Eddy Simulation is an approach for the computation of turbulent flows. The main idea of ADM is to approximate the unfiltered data in the filtered Navier–Stokes equations by deconvolution of filtered values. This is achieved via repeated filtering. Thereby problems may arise for cases where the order of the spatial discretisation scheme is too low or lower than the order of the filter operation. The interaction of the discretisation and the filtering was investigated for one–dimensional forced Burgers turbulence. For this study, both the order of the filter operator and the order of the spatial discretisation of the derivatives were varied independently. It was found that the use of ADM with low–order discretisation schemes can not be recommended. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Asymptotic study of turbulent Poiseuille flow with wall transpiration
Authors: Vigdorovich Igor , Oberlack Martin 
Published: February 2009

AbstractAn incompressible, pressure–driven, fully developed turbulent flow between two parallel walls, with an extra constant transverse velocity component, is considered. A closure condition is formulated, which relates the shear stress to the first and second derivatives of the longitudinal mean velocity. The closure condition is derived without invoking any special hypotheses on the nature of turbulent motion, only taking advantage of the fact that the flow depends on a finite number of governing parameters. By virtue of the closure condition, the momentum equation is reduced to the boundary–value problem for a second–order differential equation, which is solved by the method of matched asymptotic expansions at high values of the logarithm of the Reynolds number based on the friction velocity. A limiting transpiration velocity is obtained, such that the shear stress at the injection wall vanishes, while the maximum point on the velocity profile approaches the suction wall. In this case, a sublayer near the suction wall appears where the mean velocity is proportional to the square root of the distance from the wall. A friction law for Poiseuille flow with transpiration is found, which makes it possible to describe the relation between the wall shear stress, the Reynolds number, and the transpiration velocity by a function of one variable. A velocity defect law, which generalizes the classical law for the core region in a channel with impermeable walls to the case of transpiration, is also established. In similarity variables, the mean velocity profiles across the whole channel width outside viscous sublayers can be described by a one–parameter family of curves. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spreading of thin liquid droplets on rotating disks
Authors: Boettcher Konrad , Brandt Heiko , Ehrhard Peter 
Published: February 2009

AbstractIn many industrial processes solids are coated to obtain specific surface properties, as e.g. corrosion resistance, mechanical, optical, or electrical properties. Even today many of such coating processes are not fully understood and the choice of parameters is mainly based on experience. Hence, a prediction of the complete hydrodynamic process in its dependency on the parameters appears highly desirable. This would e.g. allow for a precise prediction of the (liquid) layer thickness and shape and help to optimize the quality of the coating. A common coating technique is the so–called spin coating. The coating agent is dissolved or suspended in a liquid, brought onto the solid, spread by rotation, and the carrier liquid is finally removed by evaporation or by chemical reactions. In this article an evolution equation is derived from lubrication theory, valid for thin liquid layers. The model involves a dynamic contact angle, centrifugal, capillary, gravitational, and molecular (London–van–der–Waals) forces. The evolution equation without molecular forces can even be solved analytically, provided the capillary number is small. Otherwise a numerical integration of the governing equations is engaged. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Steady and oscillatory analysis of porous catalysts in fluidized beds
Authors: Raja Sekhar G.P. , Prakash Jai , Kohr Mirela 
Published: February 2009

AbstractIn this paper, we consider the steady /oscillatory flow field within a porous particle contained in a fixed or fluidized bed, in which the spherical porous particle is placed in a spherical envelope of fluid. Stokes equations are employed inside the fluid envelope and Brinkman/Darcy equations are used inside the porous region. We compute drag force acting on the particle and hence the overall bed permeability of the bed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical Simulations Of Three Dimensional Glottis Flows
Authors: Klostermann Jens , Schwarze Rüdiger , Triep Michael , Brücker Christoph 
Published: February 2009

AbstractA detailed numerical investigation of the transient three dimensional flow downstream of the human glottis is performed. For the present work a threefoldly scaled up realistic static model of the vocal folds and a transient inflow function, which is obtained from experimental data is applied to the CFD model. In the numerical simulations transient flow features like forming ring vortexes and axis switching are resolved which are also known for elliptical and rectangular jets. Similar structures can also be identified in the results of the time–resolved PIV measurements. The influence of the ventricular folds and the geometrical variation of the glottis contacts are also considered in the numerical study. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical solution of turbulent jet flows
Authors: Louda Petr , Příhoda Jaromír , Kozel Karel 
Published: February 2009

AbstractThe work deals with numerical modelling of several turbulent 3D jet flows: steady impinging jet, steady free jet in cross–flow, synthetic free jet (unsteady) and synthetic impinging jet (unsteady). The numerical method is based on artificial compressibility method with dual time extension for unsteady cases. Space discretization uses cell–centered finite volume method with third order accurate upwind approximation for convection, the time discretisations are implicit. Turbulence is modelled using two–equation eddy viscosity models and by explicit algebraic Reynolds stress model (EARSM by Wallin and Hellsten). The results of first three cases are compared with measurements. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stokes‐Einstein Behaviour for Liquids with Bounded Potentials at High Densities
Authors: Mausbach P. , May H.‐O. 
Published: February 2009

AbstractBy means of molecular dynamics simulations we investigate the Stokes–Einstein behaviour of the Gaussian Core Model liquid at high densities. From a recent analysis at moderately high densities, we found that the Stokes–Einstein factor grows linearly with the viscosity. We show that at high densities the behaviour is similar, but there are slight departures at lower temperatures and higher densities. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical simulation of flows in sinusoidally‐walled channels
Authors: Weingartner B. , Kuhlmann H. 
Published: February 2009

AbstractIncompressible viscous flow in a channel with sinusoidally–walled boundaries is investigated numerically. The ultimate aim of the investigation is the computation of the linear stability with respect to two– and three–dimensional perturbations of the basic two–dimensional flow. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of fluid flow and heat transfer in coolant ducts of friction clutches
Authors: Wünsch Olaf , Mölter Stefan 
Published: February 2009

AbstractThis paper deals with the numerical simulation of the fluid flow in coolant ducts as wall as the calculation of temperature field in fluid and solid of a friction clutch. The simulations are carried out by means of commercial software based on a finite volume method in a relative framework, where the fluid flow is not time dependent. The results in dependence of rotation speed and slip velocity show interesting secondary flow in the ducts. Different flow pattern have distinct influence on the temperature field and the heat transfer. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Design of axisymmetric ducts for incompressible flow with vorticity.
Authors: Pavlika V. 
Published: February 2009

AbstractIn this paper a numerical algorithm is described for solving the boundary value problem associated with axisymmetric, inviscid, incompressible, rotational (and irrotational) flow in order to obtain duct wall shapes from prescribed wall velocity distributions. The governing equations are formulated in terms of the stream function and the function as independent variables where for irrotational flow can be recognized as the velocity potential function, for rotational flow ceases being the velocity potential function but does remain orthogonal to the stream lines. A numerical method based on finite differences on a uniform mesh is employed. The technique described is capable of tackling the so–called inverse problem where the velocity wall distributions are prescribed from which the duct wall shape is calculated, as well as the direct problem where the velocity distribution on the duct walls are calculated from prescribed duct wall shapes. The two different cases as outlined in this paper are in fact boundary value problems with Neumann and Dirichlet boundary conditions respectively. Even though both approaches are discussed, only numerical results for the case of the Dirichlet boundary conditions are given. A downstream condition is prescribed such that cylindrical flow, that is flow which is independent of the axial coordinate, exists. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)