bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical aspects on computational homogenization of epoxy/glass composites
Authors: Fleischhauer Robert , Dal Hüsnü , Kaliske Michael 
Published: December 2012

AbstractNumerical aspects of two‐scale modeling of epoxy/glass composites are presented. The homogenization process is carried out under consideration of periodic boundary constraints (PBC) of the representative volume element (RVE) due to the periodic structure of glassfiber reinforced epoxy systems. The introduction of artificial constraints for computing macro‐stresses and macro‐moduli is presented by giving the modified algorithmic treatment of a two‐scale approach using PBC. The proposed algorithm is applied to an ISO 527 epoxy/glass test specimen. The results of computations considering or not considering interphases and interfaces within the composite are compared. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Construction of Statistically Similar RVEs for 3D Microstructures
Authors: Scheunemann Lisa , Balzani Daniel , Brands Dominik , Schröder Jörg 
Published: December 2012

AbstractThis contribution presents a method to construct three‐dimensional Statistically Similar RVEs (SSRVEs) for the simulation of dual phase steel (DP steel). Since the microstructure of DP steel strongly influences the overall material properties, it should be incorporated in numerical calculations. For this purpose the FE2 method can be applied and for an efficient computation SSRVEs with a reduced complexity compared to the real microstructure have to be defined, which still represent the mechanical response of the material accurately. The construction method is based on the minimization of a least‐square functional considering suitable statistical measures describing the inclusion morphology of a given real microstructure. The mechanical response of the SSRVEs is compared to the response of the real microstructure in virtual mechanical tests. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Tolerance modelling of heat conduction in bidirectional graded thin walled cellular structures
Authors: Baron Eugeniusz , Czarnecka Sylwia 
Published: December 2012

AbstractThe aim of this contribution is to present a new method of formulation of simplified model of skeletonal structures. The exact description of the heat conduction leads to PDEs with highly oscillating and discontinuous coefficients. We would like to obtain the simplified models of the tolerance type which is described by PDEs with smooth coefficients. As a method of modelling we used the tolerance averaging. This method could be treated as a certain generalization of the well known homogenization method. However, it is not basis on the limit passage from the microstructure size to zero. This method makes it possible to analyze the effect of microstructure size on the overall i.e. macroscopic behavior of the composite structure. Instead of limit passage, we introduce here the concept of tolerance parameter. Using this concept we could define the slowly varying functions [1], [2]. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multiscale Modeling for the Simulation of Damage Processes at Refractory Materials under Thermal Shock
Authors: Henneberg Dimitri , Ricoeur Andreas 
Published: December 2012

AbstractA brittle damage model based on multiscale considerations and homogenisation procedures is presented. Cell models are developed as RVE including different microstructural features. The material laws themselves are formulated on the continuum level. Local failure occurs if the damage variable reaches a critical value. For simple configurations of the microstructure, the relation between stress, strain und temperature is derived from analytical considerations. In order to properly model the thermo‐mechanical coupling, the temperature‐dependence of material constants is taken into account. Fracture and damage mechanical approaches are combined using different techniques. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Microscopical investigation of wave propagation phenomena in residual saturated porous media
Authors: Kurzeja Patrick S. , Steeb Holger 
Published: December 2012

AbstractWave propagation is used in many fields for measurement and characterization. Corresponding multiphase models usually use a continuous approach. Nevertheless, systems like wetted rocks may be saturated residually in certain situations. In such cases, one fluid is distributed as clusters, each different in size and shape. One single, continuous phase cannot account for a variety of fluid clusters, either disconnected from each other or connected only about thin liquid films. Therefore, we present a model that considers a heterogeneous distribution of disconnected fluid clusters in the form of harmonic oscillators. These oscillators are described and distinguished by their mass, damping and eigenfrequency. Hence, the model allows to characterize different clusters and includes an additional damping mechanism due to oscillations of the fluid clusters. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Cosserat Parameter Identification within the Frame of the Discrete Element Method
Authors: Wessels Nicola , Hackl Klaus 
Published: December 2012

AbstractOne of the main challenges using the Discrete Element Method is that there is no direct compliance to the well known continuum parameters such as elastic moduli. In this article we show how homogenization procedures using representative volume elements composed of discrete particles lead to Cosserat continua.Simulating a shear test with discrete elements it becomes obvious, that the evolving microstructure is mainly composed of contact chains that form triangles and quadrilaterals. For these contact chains we set up contact energies in normal and shear directions and combine those to derive the effective energy of the material. By comparison of this energy to a Cosserat energy we can derive formulas for the Lamé and Cosserat parameters. They are now only dependent on the interaction energies and radii of the particles. To show the validity of our assumptions and derivations we present some discrete element simulations of shear tests. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Asymptotics for thin elastic fibers in unilateral contact
Authors: Bare Zoufine , Orlik Julia 
Published: December 2012

AbstractWhat is the contact condition in a 1D beam‐model and is it possible to obtain the frictional moments and forces from the 3D traction? If it is possible does the cross‐section of the beams influence these values? These questions motivate to study the dimension reduction of a 3D contact problem for beams. This paper is a continuation of [1]. In [1] the asymptotic dimension reduction of a Robin‐type elasticity boundary value problem was presented. In this work the explicit relation between a 3D contact problem and a 3D Robin‐type elasticity boundary value problem are established and the 1D equations derived in [1] are interpreted as 1D contact conditions, further some numerical examples are shown. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analytical and Numerical Modelling of the Safe Turn Manoeuvres of Agricultural Aircraft
Authors: Rašuo Boško 
Published: December 2012

AbstractIn this paper, a theoretical study of the turn manoeuvre of an agricultural aircraft is presented. The manoeuvre with changeable altitude is analyzed, together with the effect of the load factors on the turn manoeuvre characteristics during the field‐treating flights. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Preliminary results of the conditional analysis of wall friction during laminar‐turbulent transition of a rough wall boundary layer
Authors: Jonáš Pavel , Hladík Ondrej , Mazur Oton , Uruba Václav 
Published: December 2012

AbstractThe conditional analysis of the instantaneous wall friction is applied on time records made in transitional boundary layers originating on smooth surface or surface covered by sand paper (grits 60) under turbulent free stream. The applied intermittency analysis of measurement allowed the evaluations of turbulent and non‐turbulent zone averages. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Unsteady convective diffusion of a solute in a Hagen‐Poiseuille flow through a tube with permeable wall
Authors: Dumitrache Alexandru , Frunzulica Florin 
Published: December 2012

AbstractInfluence of Interphase Mass Transfer (IMT) on the unsteady convective diffusion in a fluid flow through a tube surrounded by a porous medium is examined against the background of no IMT. The three coefficients namely exchange coefficient, convection coefficient, and dispersion coefficient are evaluated asymptotically at large‐time. The exchange coefficient exists due to IMT. All‐time analysis is made analytically when there is no IMT. The mean concentration distribution is measured at a point inside and outside the slug. The peak of mean concentration is higher than that of pure convection and it is further enhanced with increase of porous parameter. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An Exact Navier‐Stokes Solution for Three‐Dimensional, Spanwise‐Homogeneous Boundary Layers
Authors: John Michael O. , Obrist Dominik , Kleiser Leonhard 
Published: December 2012

AbstractThe plane stagnation flow onto (Hiemenz boundary layer, HBL) and the asymptotic suction boundary layer flow over a flat wall (ASBL) are two boundary layer flows for which the incompressible Navier‐Stokes equations are amenable to exact similarity solutions. The Hiemenz solution has been extended to swept Hiemenz flows by superposition of a third, spanwise‐homogeneous sweep velocity. This solution becomes singular as the chordwise, tangential base flow component vanishes. In this limit, the homogeneous ASBL solution is valid, which however cannot describe the swept Hiemenz flow, because it does not contain any chordwise velocity. This work presents a generalized three‐dimensional similarity solution which describes three‐dimensional spanwise homogeneously impinging boundary layers at arbitrary wall‐normal suction velocities, using a rescaled similarity coordinate. The HBL and the ASBL are shown to be two limits of this solution. Further extensions consist of oblique impingement or different boundary suction directions, such as slip or stretching walls. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical and experimental investigation of thermal convection in an inclined narrow gap
Authors: Sommer Oliver , Heiland Hans Georg , Wozniak Günter 
Published: December 2012

AbstractThe knowledge of the fluid behaviour in inclined cavities is of fundamental importance as far as heat and mass transfer are concerned. The interest in this subject is particularly increasing due to the rapid process in micro technologies. We therefore studied the flow‐ and temperature field of such flows numerically as well as experimentally using CFD and PIV/T, respectively. We present and discuss the numerical and experimental results of our investigations and explain the applied techniques. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An Investigation of the Separate Flow and Stall‐delay for Horizontal‐Axis Wind Turbine
Authors: Frunzulica Florin , Mahu Razvan , Dumitrescu Horia 
Published: December 2012

AbstractThe flow characteristics and stall delay phenomenon of a stall regulated wind turbine rotor due to blade rotation in steady state non‐yawed conditions are investigated. An incompressible Reynolds‐averaged Navier‐Stokes solver is applied to carry out the separate flow cases at high wind speeds from 11 m/s to 25 m/s with an interval of 2 m/s. The objective of the present research effort is to validate a first‐principles based approach for modeling horizontal axis wind turbines (HAWT) under stalled flow conditions using NREL/Phase VI rotor data. The computational results are compared with the predicted values derived by a new stall‐delay model and blade element momentum (BEM) method. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Cauchy Problems and Breakdown in the Theory of Marginally Separated Flows
Authors: Aigner Mario J. , Braun Stefan 
Published: December 2012

AbstractFlow separation can be viewed as one of the trigger events of laminar‐turbulent boundary layer transition. Thus, intensive investigations have been carried out as to when and how laminar boundary layers break down. In the special case of marginal separation, i.e. the formation of short laminar separation bubbles, high Reynolds number asymptotic theory yields integro‐differential equations governing the essential flow behavior. We will present further considerations of associated initial value problems (IVPs) in planar and three‐dimensional flow cases regarding the general ill‐posedness. As for regularization methods, higher order asymptotic terms comprising the streamline curvature in the boundary layer region are taken into account rendering the hence modified problem well‐posed, which can be seen from the dispersion relation and numerical solutions of the full problem. Even though the regularized IVPs admit limiting steady states in their time evolution, the phenomenon of finite time blow‐up, which can be interpreted as “bubble bursting”, is still present for certain initial conditions. The inevitable breakdown of the asymptotic description leads to the emergence of a new asymptotic structure of shorter spatio‐temporal scales associated with the unique self‐similar blow‐up structure. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Internal Flow Analysis for Slow Moving Small Droplets in Contact with Hydrophobic Surfaces
Authors: Rasool Raheel , A. Sauer Roger , Osman Muhammad 
Published: December 2012

AbstractInternal fluid flow behavior for slow moving small droplets in contact with hydrophobic surfaces is analyzed. The shape of the droplet is first computed using the Young‐Laplace equation. For this purpose a Finite Element (FE) model [1], in which contact constraints are enforced through Penalty and Augmented Lagrange Multiplier methods, is used. The flow field within the droplet is then analyzed using the Stokes flow model, considering a de‐coupled approach. Similar to the membrane deformation model, the formulation for the flow analysis is also expressed in the framework of FE analysis. Both, stabilized (Pressure Stabilizing/Petrov‐Galerkin PSPG) and Galerkin FE formulations are considered. The motion of the fluid inside the droplet is governed by the slip condition enforced on the membrane of the droplet. Numerical examples for droplets rolling steadily are presented. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamic Mode Decomposition for Swirling Jet Flow Undergoing Vortex Breakdown
Authors: Luginsland Tobias , Kleiser Leonhard 
Published: December 2012

AbstractSwirling jets undergoing vortex breakdown occur in many technical applications, e.g. vortex burners, turbines and jet engines. At the stage of vortex breakdown the flow is dominated by a conical shear layer and a large recirculation zone around the jet axis. We performed Large‐Eddy Simulations (LES) of compressible swirling jet flows at Re=5000, Ma=0.6 in the high swirl number regime (S=1). A nozzle is included in our computational setup to account for more realistic inflow conditions. The obtained velocity fields are analyzed by means of temporal and spatial dynamic mode decomposition (DMD) to get further insight into the characteristic structures dominating the flow. We present eigenvalue spectra for the case under consideration and discuss the stability behaviour in time and space. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Multiscale Approach of Turbulent Premixed Flames treated as a Gasdynamic Discontinuity
Authors: Strein Sabine , Bruzzese Christian , Class Andreas G. 
Published: December 2012

AbstractA multiscale approach describing a turbulent flame as a gasdynamic discontinuity [1] on each scale is proposed. The methodology becomes attractive if simulations on individual scales are implemented in a very efficient way. Simulations in a 2D rectangular box with an artificial turbulence field exploiting a robust phase‐field/level‐set method fit this purpose. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Integral analysis of the flow dynamics and mass transfer in a wavy liquid film on a spinning disk
Authors: Prieling Doris , Steiner Helfried , Brenn Günter 
Published: December 2012

AbstractIn the present work the complex process of diffusion‐controlled wet chemical etching of a rotating silicon wafer is analyzed in the framework of an unsteady integral boundary layer approximation. The obtained results reproduce the waviness and the associated enhancement of the mass transfer in the wavy region, and are in good agreement with experimental findings. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Iso‐surface Computation in 3D using a graph‐theoretical Approach
Authors: Ali Abdulaziz , Bothe Dieter 
Published: December 2012

AbstractThe existing combinatorial methods for iso‐surface computation are efficient for pure visualization purposes, but it is known that the resulting iso‐surfaces can have holes, and topological problems like missing or wrong connectivity can appear. To avoid such problems, we introduce a graph‐theoretical method for the computation of iso‐surfaces on cuboid meshes in ℝ3. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of Lamb wave interaction with defects in laminated plates by SEM
Authors: Asmus Andreas , Lammering Rolf 
Published: December 2012

AbstractFor the simulation of the interaction of elastic waves in CFRP Plates with inhomogeneities and defects the spectral finite element method (SEM) is under investigation. The SEM uses high‐order shape functions which are composed of Lagrange polynomials with nodes at the Gauss‐Lobatto quadrature (GLq) points. In this way we obtain a diagonal mass matrix which makes an explicit time scheme more efficient. In a numerical example based on the first order shear deformation theory (FSDT) a computation by FEAP of an interaction with an inhomogeneity is presented. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Acoustical Performance of Concreted Wood Fiber Materials
Authors: Lumei Calin , Arghir Mariana , Tot Alin‐Cosmin 
Published: December 2012

AbstractIn this paper, an inverse acoustical characterization for determination of porosity, flow resistivity, tortuosity and other parameters of a concreted wood material was proposed. Sound absorption measurements for a concreted wood fiber material were made in an impedance tube. Four acoustical models from literature were briefly described. Each model was fitted to the experimental data in order to compute their unknown parameters. Using a least‐square method, the experimental data (sound absorption coefficient) was used to optimize the acoustical models by best‐fitting the unknown parameters. The results of this paper show that the presented technique leads to reliable estimates of the physical parameters of the material. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical Simulations of Pile Integrity Tests Using a Coupled FEM SBFEM Approach
Authors: Schauer Marco , Langer Sabine 
Published: December 2012

AbstractPiles are widely used to build a proper foundation for various buildings. The pile's quality in situ can be tested by a so called pile integrity test. In order to apply this test, an acceleration sensor is attached to the pile's head which than receives an impulse. Due to this impulse a p‐wave runs through the pile. The major part of this wave is reflected from the pile's toe and is measured by the attached acceleration sensor on top of the pile. This yields an acceleration‐time plot which has to be analysed to determine the pile's condition.Sometimes the interpretation of these plots is difficult, specially when the cross‐section of the pile is changing or is influenced by the surrounding soil. For a better understanding of this kind of measurements, numerical simulations can be performed. For these simulations a coupled finite element method (FEM) and scaled boundary finite element method (SBFEM) approach is used. This approach satisfies Sommerfeld's radiation condition and allows simulating an infinite half‐space. This ensures that the applied impulse will not to be reflected at the artificial boundary which is introduced by the boundary of the numerical discretisation. The coupled approach proposed here requires discretisation of a small domain only in contrast to a purely FEM‐based approach. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Design of Device for Determination of the Sound Absorbtion Coefficient
Authors: Tot Alin‐Cosmin , Arghir Mariana 
Published: December 2012

AbstractThis paper presents a constructive variant of acoustic impedance tube used to determine the coefficient of sound absorption materials. This alternative design brings a contribution in terms of the number of microphones mounted on the tube impedance control of acoustic vibration generator, with the calibration system of microphones mounted on the device. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Determining of Velocity Fields During Real and Experimental Simulated Beer Fermentations by UDV and LDA
Authors: Böttcher Kai , Meironke Heiko 
Published: December 2012

AbstractBeer fermentation is a very complex process, especially in the fluid‐mechanical and the biochemical point of view. Our aim is to optimize the fermentation by flow control, which requires quantities of data. The applied velocity measuring techniques should be non‐invasive to ensure that neither the flow nor the fermentation in the green beer gets influenced. Therefore, an Ultrasonic Doppler Velocimetry (UDV) system is used to determine velocity fields with 128 measuring points. It works in the turbid fluid with the existing yeast cells as tracer particles and can be applied easily to the industrial scale.For the validation of CFD‐codes and the better understanding of measurements and flow processes, model fluids are used. They can be adapted to real fluid properties like density and viscosity and allow measurements with Laser Doppler Anemometry (LDA). Another advantage over the real fluid is their fixed composition, which leads to negligible natural variations. All experiments are performed in a 270 litre fermenter. Besides the real process, measurements through optical access points and the simulation of fermentations with CO2 and heat emission are enabled. Eight individually controllable cooling zones are used as thermal actors. Resulting changes in boundary conditions induce temperature gradients and hence allow to control the flow inside the tank.This work deals with the experimental set‐up and the results on the one hand and a comparison between real and simulated fermentations on the other hand. Special attention is given to investigations of the multi‐phase flow inside the vessel and the effects of changing constraints. The usability of UDV measurement techniques is the key benefit in this case, because it can be used in green beer and model fluids and does not influence the flow. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)