bluuebunny/crossref_metadata_2025_split huggingface dataset:
Methodenentwicklung zur numerischen Strömungsanalyse von Freispiegelströmungen bei Schaufelwasserrädern
Authors: Schippke Hans‐Henning , Seidel Christian , Dinkler Dieter , Zilian Andreas 
Published: December 2014

AbstractEs wird ein Berechnungsmodell vorgestellt, mit dem eine numerische Analyse der Strömungsvorgänge innerhalb von Schaufelwasserrädern möglich ist. Das Fluidgebiet, beschrieben durch die inkompressiblen Navier‐Stokes‐Gleichungen, wird mittels der zeit‐diskontinuierlichen Raum‐Zeit‐Finite‐Elemente‐Methode diskretisiert. Die Grenzfläche Wasser‐Luft ist implizit mit Hilfe einer Level‐Set‐Funktion abgebildet, während die Grenzfläche Fluid‐Struktur direkt im Rahmen der Gebietsdiskretisierung abgebildet wird. Unter Verwendung der Shear‐Slip‐Mesh‐Update‐Methode findet die auftretende Netzbewegung Berücksichtigung. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Finite element simulation of the poling process in BaTiO3–CoFe2O4 multiferroic composites
Authors: Avakian Artjom , Gellmann Roman , Ricoeur Andreas 
Published: December 2014

AbstractThe theoretical background of nonlinear constitutive magneto‐ferroelectric behavior as well as the Finite Element implementation are presented. On this basis the polarization in the ferroelectric matrix (BaTiO3) with embedded dielectric‐magnetostrictive particels (CoFe2O4) is simulated and the resulting effects are analyzed. Numerical simulations focus on the prediction of local crystal orientations and residual stress going along with the poling process, in the future supplying information on favorable electric‐magnetic loading sequences. Further, multifield homogenization procedures enable the prediction of the electromagnetomechanical properties of smart multiferroic composites and supply useful means for their optimization. The resulting final state of a poling simulation can be implemented as a starting condition for approximate linear simulations. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Magneto‐Visco‐Elastic Model for Magnetorheological Elastomers
Authors: Ethiraj Gautam , Sridhar Ashish , Miehe Christian 
Published: December 2014

AbstractIn this work we present the modular construction and FEM implementation of a material model for magnetorheological elastomers (MRE) that is firmly rooted in micromechanics and performs well against experimental data. Keeping in mind the composite nature at the microscale, we develop a constitutive formulation based on a multiplicative magneto‐mechanical split of the deformation gradient. We consider both Lee‐ and Clifton‐type right and left decompositions. In contrast to other recent formulations [6], this general approach allows the use of highly advanced micromechnically‐based network models for polymers such as [4] and [5] in a modular format and to extend its application for coupled magnetomechanical response. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mathematical Modeling and Numerical Simulation of a Magnetostrictive Euler‐Bernoulli Beam
Authors: Harutyunyan Mané , Simeon Bernd 
Published: December 2014

AbstractMagnetostrictive (MS) materials change their mechanical behavior in response to the application of an external magnetic field and are widely used as sensors and actuators in different areas. This paper is aimed at the description of the magneto‐mechanical coupling using a model of an isotropic Euler‐Bernoulli‐beam. The simple structure of the model enables the full understanding of the effect of coupling. The main focus lies on the mathematical formulation of a coupled magneto‐elastic problem by means of a PDE with appropriate boundary conditions. The numerical modeling is performed by using the Finite Element Method. Considering linear material laws, stationary and time‐dependent cases have been analyzed. To confirm the theoretical results, corresponding simulations carried out with Matlab are presented. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Application of nonlinear continuum dislocation theory to antiplane shear
Authors: Günther Christina , Le Khanh Chau 
Published: December 2014

AbstractWe apply the nonlinear dislocation theory to the problem of antiplane constrained shear in a single crystal with one slip system. By taking dissipation into account, the relaxed energy functional has to be minimized. We show that, up to a threshold strain, no dislocations are nucleated and therefore the plastic slip is zero. Since this threshold value depends on the width of the specimen, a size effect takes place. The stress strain curve turns out to be a hysteresis loop exhibiting the work hardening due to the dislocation pile‐up. It is shown that the Bauschinger effect holds true. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling of the effective viscoelastic material behavior of textile reinforced composites using a multi‐scale approach
Authors: Branke Dominik , Kästner Markus , Pohl Martin , Ulbricht Volker 
Published: December 2014

AbstractThe increasing importance of constructive lightweight in modern engineering science involves the use of advanced materials like textile reinforced composites. In order to reduce development costs, efficient numerical simulations are needed to model the macroscopic behavior of the final product. Focussing on long term phenomena, which are important when parts made of composites with rate‐dependent material behavior are assembled by bolted or screwed joints, a two‐step homogenization procedure is used to obtain an effective homogeneous equivalent material at the macroscopic scale. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Microscale modeling and homogenization of rope‐like textiles
Authors: Fillep Sebastian , Mergheim Julia , Steinmann Paul 
Published: December 2014

AbstractThis contribution deals with rope‐like textiles. On the macroscopic level rope‐like textiles are characterized by a large length‐to‐thickness ratio, such that a discretization with beam elements is numerically efficient. To capture the contact behavior the representative volume element is explicitly modeled by means of a volumetric micro sample. A suitable, beam‐specific FE2 method is developed, which connects the homogeneous macro level to a fiber structured micro sample. This contribution investigates the determination of the nonlinear constitutive behavior of rope‐like textiles. Selected examples for the macroscopic behavior of microscopic heterogeneous fiber structured materials are presented. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Isolating low‐frequency deformations for efficient multigrid methods: a geometrically exact 2D beam model
Authors: Schröppel Christian , Wackerfuß Jens 
Published: December 2014

AbstractWe propose a novel technique for low‐frequency approximations of boundary‐value problems. In contrast to the standard Ritz‐Galerkin approach, the shape functions are given on the logarithmic space of the deformation function. The method is able to capture the complex interplay of the rotational and the translational components of the deformation. It is likely to be particularly efficient in the context of multigrid algorithms. c 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim 15
A phase‐field approach for the modeling of nematic liquid crystal elastomers
Authors: Keip Marc‐André , Bhattacharya Kaushik 
Published: December 2014

AbstractLiquid crystal elastomers combine the elastic properties of rubber with the orientational properties of liquid crystals. Amongst the various types of liquid crystal elastomers, nematic elastomers are one special class. Nematic elastomers undergo a phase transition from a high‐temperature isotropic state to a low‐temperature nematic state, which is generally accompanied by large deformations. In the present contribution, a phase‐field model for the continuum‐mechanical description of nematic elastomers will be introduced. The model is implemented into the finite element method and employed for the simulation of domain evolution under specified initial boundary conditions. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Voxel‐based fast solution of the Lippmann‐Schwinger equation with smooth material interfaces
Authors: Merkert Dennis , Andrä Heiko , Kabel Matthias , Schneider Matti , Simeon Bernd 
Published: December 2014

AbstractThe FFT‐based homogenization method proposed by Moulinec and Suquet [1] in 1994 to solve the Lippmann‐Schwinger equation has recently become more popular due to its computational speed and accuracy. It is based on regular voxel grids and can work on segmented CT images directly. Given an interface description on the sub‐voxel scale we show that using interface voxels with an appropriately chosen stiffness significantly enhances the accuracy of the computed effective properties and decreases voxelation effects in the solution. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Two Way Coupled Micro/Meso Scale Method for Wind Farms
Authors: Class Andreas , Viellieber Mathias , Moussiopoulos Nicolas , Barmpas Fotios 
Published: December 2014

AbstractWind turbines extract energy from the approaching flow field resulting in reduced wind speeds, increased turbulence and a wake downstream of the wind turbine. The wake has a multitude of negative effects on downstream wind turbines. This includes reduced efficiency and increased unsteadiness resulting in vibrations and potentially in material fatigue. Moreover, the maintenance can increase compared to non‐interfering wind turbines. The simulation of these effects is challenging. Computational fluid dynamics (CFD) simulations of these large and complex geometries requires exceedingly large computational resources. With present Reynolds Averaged Navier‐Stokes (RANS) or Large Eddy Simulation (LES) based CFD methods it is virtually impossible to perform such simulations of the interaction between individual wind turbines in a complete wind turbine farm. Coupling to the mesoscale accounting for local weather situations becomes yet more challenging. This is due to the wide range of length and time scales that have to be considered for these simulations and therefore the tremendous computational power needed to perform such simulations. To investigate these effects we propose to combine ideas from existing methods, the Coarse‐Grid‐CFD (CGCFD) ( [1]) developed at the KIT and the meso‐/ micro scale method developed at the University of Thessaloniki ( [2]). Goal of the proposed methodology is to provide a numerical method that allows to implement a wind farm in a meso‐scale weather simulation which includes two‐way coupling. Thus both the micro and the meso scale wind and energy production of wind farms can be addressed. This proposed multi scale coupling strategy can also be applied in two hierarchies reducing the numerical effort of the global approach yet more. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling and Simulation of solidification processes in polymer melt flows
Authors: Descher Stefan , Wünsch Olaf 
Published: December 2014

AbstractThis work deals with the modelling and simulation of solidification processes in polymer melt flows. Two models describing the latent heat and the rheological behaviour were implemented in a finite volume code. The models are empirical and their parameters are identified using experimental results obtained from investigations with a rotational rheometer and a differential scanning calorimetry. First results of the simulation of a solidifying channel flow are shown. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the effect of surface roughness in transonic high Reynolds number flow through slender channels
Authors: Kluwick Alfred , Kornfeld Matthias 
Published: December 2014

AbstractIn the present study transonic weakly three‐dimensional flows at high Reynolds numbers in slender channels, as they are found e.g. in micro nozzles and turbo‐machines of micro‐electromechanical‐ systems (MEMS), are considered. The channel height is taken to be so small that the viscous layers forming at the channel walls start to interact strongly rather than weakly with the predominantly inviscid core flow and, therefore, the classical boundary layer approach fails. The resulting viscous‐inviscid interaction problem is formulated using matched asymptotic expansions and found to be governed by a triple deck structure. As a consequence, the properties of the inviscid core region and the viscous wall layers have to be calculated simultaneously in the interaction region. Weakly three‐dimensional effects caused by surface roughness, upstream propagating flow perturbations and boundary layer separation are discussed. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Flow and heat transfer of non‐Newtonian fluids in enameling dies
Authors: Bari´ c Emil , Steiner Helfried , Brenn Günter 
Published: December 2014

AbstractThe present work analyses computationally the flow inside wire enameling dies within the framework of the lubrication theory approximation. Non‐Newtonian flow behavior and heat transfer are accounted for as well. It is shown that the developed approach most accurately predicts the momentum and heat fluxes along the wire. As such it is proven as a reliable and computationally efficient tool for the design of flow optimized die shapes. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Least‐squares finite element methods for the Navier‐Stokes equations for generalized Newtonian fluids
Authors: Serdas Serdar , Schwarz Alexander , Schröder Jörg , Turek Stefan , Ouazzi Abderrahim , Nickaeen Masoud 
Published: December 2014

AbstractIn this contribution we present the least‐squares finite element method (LSFEM) for the incompressible Navier‐Stokes equations. In detail, we consider a non‐Newtonian fluid flow, which is described by a power‐law model, see [1]. The second‐order problem is reformulated by introducing a first‐order div‐grad system consisting of the equilibrium condition, the incompressibility condition and the constitutive equation, which are written in residual forms, see [2]. Here, higher‐order finite elements which are an important aspect regarding accuracy for the present formulation are investigated. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
2D und 3D numerische Strömungsanalyse von Kraftwerkstrennpfeilern
Authors: Ostermann Lars , Seidel Christian 
Published: December 2014

AbstractDie numerische Untersuchung von Wasserkraftwerken ist ein wichtiges Instrument des wasserbaulichen Entwurfs und wird bei der Entwicklung und Optimierung von Wasserkraftwerken neben den experimentellen Untersuchungen am physikalischen Teilmodell oder Vollmodell im Wasserbaulabor eingesetzt. Bei den numerischen Strömungsuntersuchungen werden sowohl 2D‐ als auch 3D‐Verfahren erfolgreich verwendet. Bei den 2D‐Verfahren kommen schwerpunktmäßig vor allem flachwassergleichungsbasie Verfahren zum Einsatz, da besonders für diese Verfahren auf Grund ihrer weitverbreiteten Anwendung bei der Untersuchung strömungsmechanischer Fragestellungen im Wasserbau eine Vielzahl von Erfahrungswerten vorliegt, die häufig durch Insitu‐Messungen verifiziert sind. Die Güte der mit 2D‐Verfahren zu gewinnenden Ergebnisse bei der Optimierung von Wasserkraftwerken wird anhand der Optimierung des Kraftwerktrennpfeilers untersucht und im Vergleich mit den Ergebnissen der 3D‐Strömungsanalyse und den Experimenten am physikalischen Teilmodell gezeigt. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the possibility of using Coanda Effect for Unmanned Aerial Vehicles – a numerical investigation
Authors: Rašuo Boško , Mirkov Nikola 
Published: December 2014

AbstractIn this paper we present numerical results of conceptual design study of an UAV which uses Coanda Effect for lift production. Results indicate the ability of manuveuring by creating asymmetric flow patterns which lead to uneven lift production and resulting force with horizontal component necessary for establishing forward flight conditions. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analytical prediction for multiple roll systems with negative gaps
Authors: Willinger Bettina , Delgado Antonio 
Published: December 2014

AbstractMultiple roll coaters with deformable rolls are widely spread for the coating of thin liquid films with a wet film thickness of only a few microns and below on continuous substrates. The presented analytical solution for multiple roll systems offers for the first time the possibility to predict the performance of multiple roll coaters with a nip feed system and negative gaps. The solution is based on a previously presented solution of the authors for roll pairs and extended to multiple roll systems. The results are validated with experimental data from literature and the main influencing factors of multiple roll systems are investigated. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical Simulation of a Turbulent FSI Benchmark Case
Authors: Reimann Thorsten , Ali Awais , Sternel Dörte Carla , Schäfer Michael 
Published: December 2014

AbstractIn an effort to expand the capabilities of a validated simulation environment for fluid‐structure interaction to turbulent flows, we present the simulation of a turbulent FSI benchmark case with large displacements in a simplified two‐dimensional unsteady RANS setup. We find a fair agreement to experimental data that encourages further refinement of our approach and future three‐dimensional simulations with eddy‐resolving schemes. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Boundary Layer Heat Transport in turbulent Rayleigh‐Bénard Convection in Air
Authors: du Puits Ronald , Resagk Christian , Willert Christian 
Published: December 2014

AbstractWe study the convective heat transfer in a large‐scale Rayleigh‐Bénard (RB) experiment which is called the “Barrel of Ilmenau”. We present the results of flow visualization and Particle Image Velocimetry (PIV) measurements of the near wall flow field in a plane perpendicular to the surface of the heated bottom plate. The experiment was run in a smaller rectangular inset that was placed inside the larger barrel. The Rayleigh number amounts to Ra = 1.4 × 1010. The aspect ratios were Γx = 1 in flow direction and Γy = 0.26 perpendicular to the vertical flow plane. The measurements have been undertaken using a 2 W continuous wave Laser in combination with a light sheet optics and various cameras. Due to the slender geometry of the cell, the mean wind is confined in one direction where the Laser light sheet is aligned parallel. The flow was seeded with droplets of 1...2 µm size generated using an ordinary fog machine. Flow visualization as well as the PIV data clearly show the intermittent character of the boundary layer flow field that permanently switches between “laminar” and “turbulent” phases. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Direct Numerical Simulation of turbulent heat transfer behind a backward‐facing step at low Prandtl number
Authors: Niemann Martin , Fröhlich Jochen 
Published: December 2014

AbstractThe paper presents Direct Numerical Simulations of the turbulent flow of a low Prandtl number fluid over a backward‐facing step with heat transfer. The backward‐facing step flow is investigated as a generic configuration for sudden changes in cross section. Several simulations are reported: for isothermal conditions, for heat transfer with the Prandtl number of air, and for heat transfer with the Prandtl number of liquid sodium. The simulation for air is compared to results from literature. The differences induced by reduction of the Prandtl number are then assessed by comparison of the two cases. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Consistent implementation of real fluid EOS in pseudopotential lattice Boltzmann models
Authors: Khajepor Sorush , Dewar Marius , Wen John , Chen Baixin 
Published: December 2014

AbstractPseudopotential lattice Boltzmann models have emerged as successful methods to simulate liquid‐vapor coexistence systems. However, the equation of state (EOS) of such systems, which is found to be thermodynamically consistent, is unique and lacks the potential to cover a broad range of physical fluids. In this study, we employ multiple pseudopotentials and extend the consistent EOS to enhance the capability of pseudopotential models in reproducing a wider range of thermodynamic states. The new system has the format which preserves the consistency between the lattice pressure tensor and the free energy density. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the behaviour of thin liquid layers at curved solid edges
Authors: Sommer Oliver , Wozniak Günter 
Published: December 2014

AbstractThe knowledge of the behaviour of thin liquid layers on solid surfaces is of fundamental interest as far as basic research and applications like technical covering or lubrication processes are concerned. The subject is currently of increasing importance, particularly due to stronger requirements of thin liquid layer functionalities. We therefore studied the development of the liquid layer thickness distribution field as well as the liquid layer disturbance propagation on a plane solid surface in the vicinity of a curved solid edge experimentally using LIF technique. The investigation focusses on the influence of the initial layer thickness as well as on liquid properties like viscosity and surface tension on the liquid film behaviour, especially close to solid edges. Selected experimental results are shown highlighting relevant quantities with respect to disturbance propagation and validation. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Model Predictive Control of two‐phase flow using a diffuse interface approach
Authors: Hinze Michael , Kahle Christian 
Published: December 2014

AbstractWe propose a feedback control strategy for the stabilization of two‐phase flow with variable densities, where we use an inexact variant of Model Predictive Control, called Instantaneous Control. The physical system is governed by the Cahn–Hilliard Navier–Stokes system with different densities proposed in [1]. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stress‐driven local solution approach to quasistatic brittle delamination
Authors: Thomas Marita 
Published: December 2014

AbstractThis contribution reports on a model describing the rate‐independent evolution of brittle delamination between two elastic bodies
$\Omega_{+} \subset {\rm I\!R}^{d}$
and
$\Omega_{-} \subset {\rm I\!R}^{d}, d \geq 2$
, bonded along a prescribed contact surface
$\Gamma_{C} \subset {\rm I\!R}^{d-1}$
, over a fixed time interval (0, T). In contrast to [1], which is set in the framework of energetic solutions, here the existence and properties of so‐called local solutions are studied; a detailed discussion and a rigorous mathematical analysis of this model can be found in [2]. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The sensitivity of optimal states to time delay
Authors: Gugat Martin , Herty Michael 
Published: December 2014

AbstractIn the design and computation of optimal controls for systems that evolve in time, usually the effect of delay is ignored. However in the implementation of the computed optimal controls in the control systems often delays occur, for example through transmission via digital communication channels. The question to be addressed is whether such small delays can have large effects on a system that is steered by an optimal control. We show that for a system that is governed by the wave equation with L2‐norm minimal exact Dirichlet boundary control, for arbitrarily small time‐delays there are initial states such that the terminal energy is almost twice as big as the initial energy. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)