bluuebunny/crossref_metadata_2025_split huggingface dataset:
Linear and nonlinear Finite Element modeling of coupled electro‐magneto‐mechanical multifield problems
Authors: Avakian Artjom , Ricoeur Andreas 
Published: November 2013

AbstractIn this paper we present the theoretical background and application of Finite Element algorithms for linear and nonlinear problems of multiple field coupling. They enable the prediction of the electromagnetomechanical behavior of materials and structures and supply useful tools for the optimization of multifunctional composites. First, linear three‐field coupling is presented within the context of a Finite Element implementation. Then, a homogenization procedure is discussed. Finally, a micromechanical model for nonlinear ferroelectric constitutive behavior and its numerical realization are outlined. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High‐order time‐integration applied to p‐version finite elements within finite strain thermo‐viscoelasticity
Authors: Hartmann Stefan , Netz Torben 
Published: November 2013

AbstractIn this essay a fully coupled, monolithic thermo‐mechanical coupled simulation using high‐order finite elements based on hierarchical shape‐functions in combination with a high‐order time‐integration scheme using diagonally‐implicit Runge‐Kutta schemes is presented. The constitutive model is based on a finite strain thermo‐viscoelasticity relation of overstress‐type. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Energy‐Conserving Data Transfer in the Partitioned Treatment of Thermo‐Viscoplastic Problems
Authors: Erbts Patrick , Rothe Steffen , Düster Alexander , Hartmann Stefan 
Published: November 2013

AbstractPartitioned coupling approaches are a well‐established solution strategy for the numerical treatment of multi‐physical problems. The nature of the decoupled algorithm requires a repetitive data exchange to achieve a proper balance between the different fields concerned. In the case of non‐matching meshes, the data transfer becomes of particular importance when the values of interest are only available at the local integration points. In this case, an additional interpolation scheme has to be initialized in order to assure an energy‐conserving data transfer. This contribution looks at a thermo‐viscoplastic material that requires the interpolation of history‐dependent data onto the thermal mesh. We propose a technique employing a least‐square fit procedure and present a numerical example demonstrating the accurate data transfer. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Degree of cure‐dependent modelling for polymer curing processes at small strains
Authors: Hossain Mokarram , Saxena Prashant , Steinmann Paul 
Published: November 2013

AbstractIn this paper, a thermodynamically consistent small strain constitutive model is formulated that is directly based on the degree of cure, a key parameter in the curing (reaction) kinetics. The new formulation is also in line with the earlier proposed hypoelastic approach, cf. Hossain et al., 2010. The curing process of polymers is a complex phenomenon involving a series of chemical reactions which transform a viscoelastic fluid into a viscoelastic solid during which the temperature, the chemistry and the mechanics are coupled. Some representative numerical examples conclude the paper and show the capability of the newly proposed constitutive formulation to capture major phenomena observed during the curing processes of polymers. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
FE‐Analysis of concentration dependent healing processes in a polymer matrix
Authors: Specht Steffen , Bluhm Joachim , Schröder Jörg 
Published: November 2013

AbstractIn this contribution, a macroscopic four‐phase model, based on the Theory of Porous Media, is presented to simulate healing processes in a polymer matrix which depend on the amount (concentration) of catalysts. Therefore, the healing process is described by the phase transition from liquid like healing agents to solid like healed material. This phase transition is a function depending on the concentration. To show the applicability of the developed model, a numerical example will be presented. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Methodenentwicklung zur numerischen Strömungsanalyse von Schaufelwasserrädern
Authors: Schippke Hans‐Henning , Seidel Christian , Zilian Andreas , Dinkler Dieter 
Published: November 2013

AbstractEs wird ein Berechnungsmodell vorgestellt, mit dem eine numerischen Analyse der Strömungsvorgänge innerhalb von Schaufelwasserrädern möglich ist. Der Arbeitsschwerpunkt liegt dabei auf der strömungsmechanischen Optimierung von Hochleistungswasserrädern der Weiterentwickelten Wasserradtechnologie. In dem Berechnungsmodell werden die inkompressiblen Navier‐Stokes‐Gleichungen in den unabhängigen Variablen Geschwindigkeiten und Druck mit Hilfe der zeit‐diskontinuierlichen Raum‐Zeit‐Finite‐Elemente‐Methode diskretisiert und die auftretende Gebietsveränderung infolge der sich drehenden Struktur mit der Shear‐Slip Mesh Update Methode als diskontinuierlichem Netzbewegungsverfahren erfasst. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Computational Modeling of Liquid Droplets Moving on Rough Surfaces
Authors: Rasool Raheel , Osman Muhammad , A. Sauer Roger 
Published: November 2013

AbstractWe present a de‐coupled approach for computational modeling of liquid droplets moving on rough substrate surfaces. The computational model comprises solving the membrane deformation problem and the fluid flow problem in a segregated manner. The droplet shape is first computed by solving the Young‐Laplace equation where contact constraints, due to the droplet‐substrate contact, are applied through the penalty method [1]. The resulting configuration constitutes the domain for the fluid flow problem, where the bulk fluid behavior is modeled by the unsteady Stokes' flow model expressed in Arbitrary Lagrangian‐Eulerian (ALE) framework. The entire analysis is performed in the framework of Finite Element Method (FEM). Application of the approach to the case of a droplet moving on a rough surface is presented as an example. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Coupled Multi‐field and Multi‐rate Problems – Numerical Solution and Stability Analysis
Authors: Zinatbakhsh Seyedmohammad , Markert Bernd , Ehlers Wolfgang 
Published: November 2013

AbstractThe numerical solution of coupled differential equation systems is usually done following a monolithic or a decoupled algorithm. In contrast to the holistic monolithic solvers, the decoupled solution strategies are based on breaking down the system into several subsystems. This results in different characteristics of these families of solvers, e. g., while the monolithic algorithms provide a relatively straight‐forward solution framework, unlike their decoupled counterparts, they hinder software re‐usability and customisation. This is a drawback for multi‐field and multi‐rate problems. The reason is that a multi‐field problem comprises several subproblems corresponding to interacting subsystems. This suggests exploiting an individual solver for each subproblem. Moreover, for the efficient solution of a multi‐rate problem, it makes sense to perform the temporal integration of each subproblem using a time‐step size relative to its evolution rate. Nevertheless, decoupled solvers introduce additional errors to the solution and, thus, they must always be accompanied by a thorough stability analysis.Here, tailored solution schemes for the decoupled solution of multi‐field and multi‐rate problems are proposed. Moreover, the stability behaviour of the solutions obtained from these methods are studied. Numerical examples are solved and the reliability of the outcome of the stability analysis is investigated. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Estimation of large domain Al foam permeability by Finite Difference methods
Authors: Osorno Maria , Steeb Holger , Uribe David , Ruiz Oscar 
Published: November 2013

AbstractClassical methods to calculate permeability of porous media have been proposed mainly for high density (e.g. granular) materials. These methods present shortcomings in high porosity, i.e. high permeability media (e.g. metallic foams). While for dense materials permeability seems to be a function of bulk properties and occupancy averaged over the volume, for highly porous materials these parameters fail to predict it. Several authors have attacked the problem by solving the Navier‐Stokes equations for the pressure and velocity of a liquid flowing through a small domain (Ωs) of aluminium foam and by comparing the numerical results with experimental values (prediction error approx. 9%). In this article, we present calculations for much larger domains (ΩL) using the Finite Difference (FD) method, solving also for the pressure and velocity of a viscous liquid flowing through the Packed Spheres scenario. The ratio Vol(ΩL)/Vol(Ωs) is around 103. The comparison of our results with the Packed Spheres example yields a prediction error of 5% for the intrinsic permeability. Additionally, numerical permeability calculations have been performed for Al foam samples. Our geometric modelling of the porous domain stems from 3D X‐ray tomography, yielding voxel information, which is particularly appropriate for FD. Ongoing work concerns the reduction in computing times of the FD method, consideration of other materials and fluids, and comparison with experimental data. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling reorientation phenomena in nonwoven materials with random fiber network microstructure
Authors: Raina Arun , Linder Christian 
Published: November 2013

AbstractIn this work, a micromechanically motivated affine full network model (AFNM) is used to simulate the load‐displacement response of nonwoven materials. These materials are made from synthetic advanced fibers by bonding or interlocking networks of randomly laid fibers through mechanical, chemical or thermal processes. This results into a random fibrous network microstructure and a highly inhomogeneous response to external loadings with a very high degree of anisotropy. The load‐displacement response under large strains is observed to be highly non‐linear with a stiffening behavior which is also accompanied by complex dissipative phenomena. The preliminary simulation results with the AFNM, after reducing to two‐dimensional setting, highlight its limitations and help identify the areas of improvement for a realistic material modeling. Reorientation of fibers are shown to play a critical role in the overall macroscale response of the materials. A new evolution law for reorientation is presented in the form of a first order ordinary differential equation where an exact analytical solution to the same is also computed. Improvements of the predicted load‐displacement response signify the microscopic origins of the non‐linear stiffening behavior as reorientation of fibers. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Generalized boundary conditions on representative volume elements and their use in determining the effective material properties
Authors: Glüge Rainer 
Published: November 2013

AbstractWe discuss generalized boundary conditions for representative volume elements (RVE), which include the classical boundary conditions as special cases. From the generalization, stochastic boundary conditions are derived. These allows to adjust the the stiffness of the boundary conditions smoothly between the extremal cases of homogeneous strain and homogeneous stress boundary conditions. We found that it needs to be distinguished between the resistance of the boundary conditions against homogeneous and inhomogeneous RVE deformation. The stochastic BC can combine the moderate stiffness of the well known periodic boundary conditions with the high resistance against localization of the homogeneous strain boundary conditions. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Non‐linear deformation properties of materials with stochastically distributed anisotropic inclusions
Authors: Nazarenko Lidiia , Bargmann Swantje , Khoroshun Leonid 
Published: November 2013

AbstractIn the present contribution, the problem of non‐linear deformation of materials with stochastically distributed anisotropic inclusions is considered on the basis of the methods of mechanics of stochastically non‐homogeneous media. The homogenization model of materials of stochastic structure with physically non‐linear components is developed for the case of a matrix which is strengthened by unidirectional ellipsoidal inclusions. It is assumed that the matrix is isotropic, deforms non‐linearly; inclusions are linear‐elastic and have transversally‐isotropic symmetry of physical and mechanical properties. Stochastic differential equations of physically non‐linear elasticity theory form the underlying equations. Transformation of these equations into integral equations by using the Green's function and application of the method of conditional moments allow us to reduce the problem to a system of non‐linear algebraic equations. This system of non‐linear algebraic equations is solved by the Newton‐Raphson method. On the analytical as well as the numerical basis, the algorithm for determination of the non‐linear effective characteristics of such a material is introduced. The non‐linear behavior of such a material is caused by the non‐linear matrix deformations. On the basis of the numerical solution, the dependences of homogenized Poisson's coefficients on macro‐strains and the non‐linear stress‐strain diagrams for a material with randomly distributed unidirectional ellipsoidal pores are predicted and discussed for different volume fractions of pores. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical analysis of two‐phase magneto‐electric composites
Authors: Labusch Matthias , Keip Marc‐André , Schröder Jörg , Lupascu Doru C. 
Published: November 2013

AbstractThe focus of this paper is on the simulation of two‐phase magneto‐electric (ME) composites, consisting of a piezoelectric matrix with piezomagnetic inclusions. In such composites, the coupling between electric and magnetic fields is strain‐induced and thus ME coupling arises as a product porperty. In order to compute the effective properties of the composite a computational homogenization scheme based on the Finite Element Method will be applied. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Homogenization of Elastic Properties of Short Fiber Reinforced Composites Based on Discrete Microstructure Data
Authors: Müller Viktor , Böhlke Thomas , Dillenberger Felix , Kolling Stefan 
Published: November 2013

AbstractSince the microstructure of short fiber reinforced composites is inhomogeneous, the application of micromechanical models is useful, that take into account their characteristics like the fiber orientation and the aspect ratio of fibers. Two different methods are considered in this work: A two‐step approach is utilized to get approximately the upper and lower bounds of the elastic properties. Furthermore, an approximation for the elastic properties is calculated by the self‐consistence method. Both methods use discretely microstructural information including the length, the diameter and the orientation of each single fiber. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Linking Micro‐ and Macroscopic Aspects of a Dislocation Based Continuum Model by Investigating the Dislocation Double Pileup
Authors: Schmitt Severin , Schulz Katrin , Dickel Doyl , Gumbsch Peter 
Published: November 2013

AbstractIn this contribution we discuss the problem of a dislocation double pileup at impenetrable boundaries which serves as a benchmark test to examine the continuum dislocation dynamics (CDD). We enhance a formulation for a numerical implementation and the mean‐field theory to account for the ‘long‐range’ stress field due to inhomogeneous plastic deformations by a suitable correction term. This allows us to handle the motion of dislocation densities at impenetrable boundaries and study the influence of dislocation interactions on a scale much smaller than the scale of the proposed mean‐field stress. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of pitching on performance of VAWTs
Authors: Bogateanu Radu , Dumitrache Alexandru , Cardos Vladimir , Dumitrescu Horia 
Published: November 2013

AbstractSelf‐ starting is the major obstacle to be overcome for successful design of a vertical axis wind turbine (VAWT). In the past has been suggested that pitching the turbine blades such that pitch angle is not 90 degrees allows for self‐starting. To understand the physics surrounding pitching, an analysis is carried out for a common airfoil profile, NACA 0012. The vortex model is used to predict aerodynamic performance of VAWT with pitched blades at various angles. As a result of the analysis carried out for the airfoil at various pitch angles, it was shown that the “dead band” phenomenon could be overcome, but only slightly. At the same time, to overcome the “dead band” with a level on confidence, torques in the tip speed ratio (TSR ) range of 0.75 to 2.75 must be increased to values further above zero. The paper aimed at giving an insight into the small wind turbine starting behavior and its influence parameters. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The boundary layer in the hub area of wind turbine blades at high wind speeds
Authors: Dumitrescu Horia , Cardos Vladimir , Frunzulica Florin 
Published: November 2013

AbstractAt low tip speed ratios, the strongest effect at the inboard half‐span, when a vortex like flow occurs, is produced. These 3‐D rotational effects contribute to a stall delay as well as higher lift and angles of attack at the inboard sections, as compared to 2‐D flow conditions. A greater understanding of the mechanisms and properties of the shear layer close to the upper side surface of blade is sought through the development of an analytic theory and then is completed by CFD computations. The results show that the secondary flow has a slip effect on the blade surface and its circumferential velocity is less than that of blade revolution, particularly important for TSR <3.0. While at the high tip speed ratios the flow around the blade is much as the 2‐D one, then at the low tip speed ratios, TSR < 3.0 the flow behaves rather like the impinging flow on a rotating disc. Therefore, the 3‐D rotational effects dominate the flow at high wind speeds and a special approach of such flows would be to assume. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Non‐linear Proper Orthogonal Decomposition Reduced Order Modeling: Bifurcation Study of a Natural Convection Circuit
Authors: Prill Dennis P. , Class Andreas G. 
Published: November 2013

AbstractBoiling water reactors (BWRs) not only show growing power oscillations at high‐power low‐flow conditions but also amplitude limited oscillations with temporal flow reversal. Methodologies, applicable in the non‐linear regime, allow insight into the physical mechanisms behind BWR dynamics. The present paper aims at a general non‐linear methodology capable to achieve reliable and numerical stable reduced order models (ROMs). Model‐specific options and prediction capabilities are adressed and illustrated by means of two strongly non‐linear dynamical systems: Firstly, the tubular reactor (TR), treated as a generic “pathologic” test case for perturbation investigations violating the inlet conditions, and secondly, the natural convection in a closed circuit (NCC), considered due to dynamical similarities to BWRs. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A model for fluid flow in non‐fully filled tribological interfaces – Part 1: Basics and Numerics
Authors: Müller Michael , Bubser Florian , Ostermeyer G.‐P. 
Published: November 2013

AbstractIn literature, most contributions on starved lubrication focus on the occurring pressures in macroscopic devices. Hereby, usually the Reynolds equation is modified in different ways. In contrast to this proceeding, this paper's intention is the general investigation of this tribological regime to get a fundamental comprehension on the transition from boundary lubrication to mixed lubrication. The respective model describes the flow of the fluid through two rough surfaces moving relative to each other. The lack of fluid is regarded by the fact that elements may not be fully filled with the fluid. Only elements where the fluid fully fills the gap, generate a pressure. This effect is considered by a type of unilateral constraint in combination with a penalty function. The fluid flow is computed according to the Navier‐Stokes equation. In combination with the continuity equation, a set of implicit nonlinear equations has to be solved. Its potential and basic application fields are finally discussed. A further paper will show applications of the algorithm towards different scenarios. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical Simulation of Turbulent Swirling Flows
Authors: Ćoćić Aleksandar , Pritz Balazs , Gabi Martin , Lečić Milan 
Published: November 2013

AbstractIn this paper, turbulent swirling flow in circular pipe in the wake behind an axial fan is investigated by URANS and LES using two different CFD codes: SPARC, developed at Institute of Fluid Machinery, at Karlsruhe Institute of Technology and OpenFOAM. Results of simulations are compared with experimental results obtained with LDA measurement techniques in that flow field. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical and experimental investigation of the turbulent flow through a low‐pressure turbine cascade in the endwall region
Authors: Koschichow Denis , Fröhlich Jochen , Ciorciari Roberto , Kirik Ilker , Niehuis Reinhard 
Published: November 2013

AbstractIn the present work, direct numerical simulations (DNS) of the flow through a low‐pressure linear turbine cascade T106 with parallel endwalls were conducted to investigate the effects of unsteady passing wakes of the upstream blade row on the secondary flow in the endwall region of the passage. The impact of the wakes on the secondary flow is discussed by means of the time‐averaged values. Furthermore, the results of DNS are compared with experimental data. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of Mass Loading on Particle‐Laden Turbulent Pipe Flow
Authors: Reinhardt Yvonne , Kleiser Leonhard 
Published: November 2013

AbstractA CFD code in the framework of OpenFOAM was validated for simulations of particle‐laden pipe and channel flows at low to intermediate mass loadings. The code is based on an Eulerian two‐fluid approach with Reynolds‐averaged conservation equations, including turbulence modeling and four‐way coupling. Pipe flow simulations of particles in air against gravity were conducted at Reynolds numbers up to 50000. The particle mass loading was varied and its effect on the mean velocities and turbulent fluctuations of the two phases was studied. Special attention was paid to the influence of mass loading on the centerline velocity and the wall shear velocity of the fluid phase for various flow parameters and particle properties. Empirical correlations were established between these two quantities and the flow Reynolds number, particle Reynolds number, Stokes number and particle to fluid density ratio for a range of particle mass loadings. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)