bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis and modeling of the hydro‐mechanics of deformable fractures
Authors: Vinci Carlo , Renner Jörg , Steeb Holger 
Published: December 2012

AbstractIn the present contribution, we investigate and model the flow of a viscous fluid into a single deformable fracture and the associated elastic deformation of the surrounding porous rock. Due to the coupled nature of the problem, conceptually and technically different strategies can be applied to model and solve the resulting hydro‐mechanical system. Therefore, two different modeling approaches are analyzed. On the one hand, we derive the governing equations from the conservation of mass avoiding any of the frequently used approximations or simplifications. On the other hand, we describe the physics based on Biot's quasi‐static poroelastic equations. We compare and critically discuss the results obtained with the presented different solution approaches. The results show that both models are able to capture the same physical effects, also those caused by the fracture deformation. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multiphase FEM Modeling of Infiltration Processes in Cohesionless Soils
Authors: Schaufler A. , Becker C. , Steeb H. 
Published: December 2012

AbstractThe aim of this work is to develop a continuum multiphase model to describe infiltration processes for cohesionless soils. For this purpose, a Representative Volume Element (RVE) is considered and described by the continuum mixture theory extended by the concept of volume fractions (Theory of Porous Media – TPM). The thermodynamically consistent TPM is a macroscopical multiphase modeling approach, extended from classical single‐phase continuum mechanics. Futhermore a 1‐dim example for an infiltration problem is presented. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A three‐phase model for polymer curing including diffusive motion and agglomeration of inclusions.
Authors: Lenhof Bernd , Diebels Stefan 
Published: December 2012

AbstractIn this work, a phenomenological three‐phase model is formulated to simulate agglomeration and breakup of particles contained in a polymer. It shall serve as a starting point for modelling the same phenomena in curing polymers. While isothermal processes are assumed, the model is stated in the framework of continuum mechanics of mixtures. The phenomenological model consists of a polymer phase, and two particle phases. Agglomeration and breakup is modeled as a concentration exchange between the two particle phases. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mechanical behavior of a pH‐sensitive hydrogel ring used in a micro‐optical device
Authors: Zalachas Nicolas , Cai Shengqiang , Suo Zhigang , Lapusta Yuri 
Published: December 2012

AbstractA hydrogel is a polymer network that can absorb a large quantity of solvent and swell due to a physical or chemical stimulus. Hydrogels are more and more used as smart materials in recent micro‐applications. This fact requires the development of adequate models and simulation tools for their large deformation behavior. These models must also predict the onset of instabilities, such as folding or creasing. In this work, we study an interesting application of adaptive optical microsystem using a previously developed theory of inhomogeneous large deformation of a pH‐sensitive hydrogel. The devices function is based on the swelling of a ring made of a pH‐sensitive hydrogel. The latter controls the focal length of the liquid microlens. Our aim is to analyze major design parameters that affect the hydrogel ring behavior and the function of the micro‐optical device. The problem is solved numerically with the finite element commercial software ABAQUS. Various modes of large deformation and the influence of the rings aspect ratio on the behavior of the micro‐device are investigated. Results show that, for relatively short rings, a stable swelling takes place. Rings with a relatively big aspect ratio can have an unstable swelling with the propagation of a creasing instability. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A model of the heat conduction for functionally graded laminate with uniformly distributed micro inclusions
Authors: Wągrowska Monika , Woźniak Czesław , Szlachetka Olga 
Published: December 2012

AbstractThe aim of the contribution is to formulate an asymptotic model of heat conduction for functionally graded two component laminate reinforced by periodically spaced micro inclusions. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Homogenization of random elastic networks with non‐affine kinematics
Authors: Tkachuk Mykola , Linder Christian 
Published: December 2012

AbstractThis contribution concerns the mechanics of materials with random network microstructures. It develops a general homogenization approach that allows to link the microscopic deformation of fibers in the disordered network with the macroscopic response of the continuous solid. This link is established by a novel micro‐macro relation based on the kinematics of maximal advance paths that constrains the unknown microscopic stretch of fibers with respect to the macroscopic strain. This relation accounts for the topology of the network, in particular, its connectivity and takes for the tetrafunctional networks a clearly interpretable tensorial form. In line with the principle of the minimum averaged free energy the elastic response of the network is obtained by the relaxation of the variable fiber stretch subjected to the kinematic constraint. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Local probabilistic homogenization schemes for assessment of material uncertainties in solid foams
Authors: Hohe Jörg , Beckmann Carla 
Published: December 2012

AbstractThe present study is concerned with a numerical scheme for prediction of the effective properties of solid foams considering their uncertainty. The approach is based on an analysis of a large‐scale, statistically representative volume element which is subdivided into small‐scale testing volume elements. Application of a standard homogenization scheme to the testing volume elements together with a stochastic evaluation yields a complete probabilistic characterization of the material which may be used for a random field definition of the material behaviour in a macroscopic effective field analysis of foam structures. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A stochastic homogenization scheme for damaged composites
Authors: Hürkamp André , Nackenhorst Udo 
Published: December 2012

AbstractA stochastic homogenization scheme for the computation of effective elastic properties for damaged micro‐heterogeneous materials is presented. The statistics is captured by uncertain material properties as well as stochastic interpolation between the upper and lower Hashin‐Shtrikman bounds. The resulting multidimensional stochastic problem is solved via sophisticated Monte Carlo methods and applied to Ultra‐High‐Performance‐Concrete. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Near critical laminar flow past an expansion ramp
Authors: Kluwick Alfred , Braun Stefan , Szeywerth Rene 
Published: December 2012

AbstractSteady two‐dimensional laminar flows past an expansion ramp are known to exist up to a critical ramp angle in the limit c as the Reynolds number tends to infinity. The theory of viscous‐inviscid interaction combined with a local bifurcation analysis is used to study the evolution of three‐dimensional unsteady perturbations if $|\alpha - \alpha_c| \ll 1$ for both sub‐ and supercritical conditions. Special emphasis is placed on the effects of controlling devices and the phenomenon of bubble bursting. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Asymptotic description of incipient separation bubble bursting
Authors: Braun Stefan , Scheichl Stefan , Kluwick Alfred 
Published: December 2012

AbstractThe appearance of short laminar separation bubbles in high Reynolds number (Re) wall bounded flows due to appropriate adverse pressure gradient conditions is usually associated with minor effects on global flow properties (e.g. lift force). However, localized reverse flow regions are known to react very sensitively to perturbations and in further consequence may trigger the laminar‐turbulent transition process or even cause global separation. The present investigation of marginally separated boundary layer flows is based on an asymptotic approach Re → ∞. Special emphasis is placed on solutions of the corresponding model equations which blow up within finite time indicating the ejection of a vortical structure and the emergence of shorter spatio‐temporal scales reminiscent of the early transition scenario (‘ bubble bursting’ ). Within the framework of marginal separation theory, an alternative adjoint operator method is used to formulate evolution equations governing the viscous‐inviscid interaction process in leading and higher order correction required for the study of later stages of the flow development. Their blow up structure specifies the initial condition of and the match to the subsequent triple deck stage. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulating of a pressing process of a viscoelastic polymer melt
Authors: Al‐Baldawi Ammar , Wünsch Olaf 
Published: December 2012

AbstractA well known and often used method to obtain anisotropic polymer films is the so‐called pressing process. Here, films are squeezed under high temperatures, pressure and deformation rates. To simulate such a process, the polymeric matrix is treated as a non‐Newtonian, viscoelastic melt. The modeling of such melts is done with the anisotropic molecule movement tensor generalization of the Maxwell Model for high deformation rates. The viscoelastic flow simulations are done with DEVSS stabilization techniques and an ALE based dynamic mesh Method. In this work we present simulations in order to show the difference between classical approaches using a generalized Newtonian viscosity to model the melt and the used viscoelastic models. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Separation of magnetic particles in channel flows by BEM
Authors: Ravnik Jure , Hriberšek Matjaž , Vogel Franziska , Steinmann Paul 
Published: December 2012

AbstractIn‐line separation of suspensions can become difficult in case of particles with comparable values of densities. For flows in micro devices in such cases gravitational settling is inefficient, and other separation techniques must be applied. In case of magneto active particles, the action of Kelvin magnetic force in a non‐uniform magnetic field could be used in order to achieve a higher degree of particles separation. The contribution therefore deals with Euler‐Lagrangian formulation of dilute two‐phase flows. The Boundary element based computational algorithm solves the incompressible Navier‐Stokes equations written in velocity‐vorticity formulation. The non‐uniform magnetic field is defined analytically for the case of a set of long thin wires. The particle trajectories are computed by applying the 4th order Runge‐Kutta method. The computed test case consists of a narrow channel with laminar flow of suspension under Re = 1 − 10. Particle trajectories under the influence of a non‐uniform magnetic field are computed for the case of magnetite and aluminium particles suspended in water. The efficiency of separation on basis of particle trajectories for different values of Re number and magnetic field strength is performed, clearly indicating superior separation of magneto active particles. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Flow over back‐facing step in a narrow channel
Authors: Uruba Václav , Jonáš Pavel 
Published: December 2012

AbstractFlow structure behind the backward facing step in a narrow channel was studied in details. The step height was 25% of the channel width. The structure of the region just behind the step forming the back‐flow region is studied in details using stereo PIV technique. Time‐mean 3D structures behind the step are evaluated and shown in the paper. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Free energy budgets in viscoelastic natural convection
Authors: De Angelis Elisabetta 
Published: December 2012

AbstractIt has been known for a long time that the introduction of a small amount of polymer additives could significantly reduce friction drag in wall‐bounded turbulent flows [1]. However, in the last years also the effect of polymers on turbulent thermal convection has drawn attention with controversial results. In this context, aim of this contribution is the presentation of the mathematical model for the study of natural convection between parallel walls in a dilute polymer solution. The discussion here will be also extended to the description of the kinetic and free energy balances in this flow. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Two‐Phase Flow in Single‐Screw Extruders
Authors: Lübke Martin , Wünsch Olaf 
Published: December 2012

AbstractThis work concerns numerical simulation of free‐surface flows of highly viscous liquids in single‐screw extruders.The numerical treatment of a partially filled extruder is a challenging task due to the complex geometry and the large differences in density and viscosity between the two phases, e.g. polymer melt and air. Furthermore, the rotation of the screw leads to a continuous renewing of the free‐surface. For this purpose the Volume of Fluid (VOF) method is used. First a simplified two‐dimensional model of a single‐screw extruder is considered. Good agreement is obtained between the numerical results and experimental data. Finally, the three dimensional free‐surface flow in a partially filled single‐screw extruder with dynamic mesh motion is presented. In addition, the power characteristics of a conveying screw element with varying degree of filling is discussed. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical study of a liquid/liquid slug flow in a micro‐reactor
Authors: Dittmar Ina , Ehrhard Peter 
Published: December 2012

AbstractThe great advantages of micro–reactors are associated with an extremely high surface–to–volume ratio. Hence, micro–reactors permit promising operating conditions, such as almost perfect heat or mass transfer. The hydrodynamics of a liquid/liquid slug flow in a micro–channel is characterized by complex vortex structures in both the disperse and the continuous phase. The disperse phase, in our investigations, is not wetting the walls and, thus, a thin film of the continuous phase persists between the disperse phase and the wall. Due to this phenomenon, a relative movement between disperse and continuous phase is possible and, indeed, observed. Understanding of these complex phenomena allows for a control of the hydrodynamics, and thus, to tailor the heat and mass transport in a desired manner. To study the physics of this complex liquid/liquid system, a modified level–set method in conjunction with an immersed–boundary formulation is engaged. The mesh resolution represents a challenge, as the spatial resolution has to resolve the thin film between the disperse phase and the wall adequately. All simulations are implemented within the software OpenFOAM. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical study of the primary breakup of a plane liquid sheet with co‐flowing air streams
Authors: Kannan Suresh kumar , Peters Bernhard 
Published: December 2012

AbstractThe objective of this study is to model the primary breakup of a plane liquid sheet emerging from an air‐blast nozzle. In the present work the interface compression scheme proposed by OpenCFD Ltd. [1] has been used to capture the interface between the liquid and gas. A One‐equation subgrid scale (sgs) turbulent energy transport model attributed to Yoshizawa [2] is used for modeling the effects of turbulence. The set up case selected for this study is based on the experiments carried out by Mitra [3]. The 2D simulations performed in this study predict the breakup length of the plane liquid sheet in good agreement with the experimental data. Future work will involve, performing 3D simulations of the plane liquid sheet generated by the air‐blast nozzle and performing comparisons of the resulting droplet characteristics with the experimental data. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
ALE‐FEM For Two‐Phase Flows With Insoluble Surfactants
Authors: Hahn Andreas , Tobiska Lutz 
Published: December 2012

AbstractWe present a finite element method for the flow of two immiscible incompressible fluids in two and three dimensions. Thereby the presence of surface active agents (surfactants) on the interface is allowed, which alter the surface tension. The model consists of the incompressible Navier‐Stokes equations for velocity and pressure and a convection‐diffusion equation on the interface for the distribution of the surfactant. A moving grid technique is applied to track the interface, on that account a Arbitrary‐Lagrangian‐Eulerian (ALE) formulation of the Navier‐Stokes equation is used. The surface tension force is incorporated directly by making use of the Laplace‐Beltrami operator technique [1]. Furthermore, we use a finite element method for the convection‐diffusion equation on the moving hypersurface. In order to get a high accurate method the interface, velocity, pressure, and the surfactant concentration are approximated by isoparametric finite elements. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the coupling of compressible and incompressible regions
Authors: Boger Markus , Jaegle Felix , Klein Rupert , Munz Claus‐Dieter 
Published: December 2012

AbstractThis contribution deals with the coupling of compressible to incompressible flow regions in one space dimension. Iterative coupling procedures based on jump conditions across the interface have been derived. They couple the solution of a half Riemann problem on the compressible side to the analytical solution of the incompressible side. For the incompressible equations, the pressure is split into a thermodynamic background and a hydrodynamic part. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical computation of dispersion relations in wave guides
Authors: Gravenkamp Hauke , Song Chongmin , Prager Jens 
Published: December 2012

AbstractIn this paper a numerical approach, based on the Scaled Boundary Finite Element Method (SBFEM), is described to obtain dispersion relations for propagating modes in wave guides. While the formulation is developed for plate structures, it can easily be extended to wave guides with arbitrary cross‐section. The cross‐section is discretized in the Finite Element sense while all equations remain analytical in the direction of propagation. The wave numbers of all propagating modes are obtained as the solutions of a standard eigenvalue problem. The group velocities can be calculated accurately as the eigenvalue derivatives. The use of higher‐order elements drastically increases the efficiency and accuracy of the computation. This approach can be used for wave guides with arbitrary distribution of material parameters. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dispersion in Cylindrical Waveguides with Uncertain Parameters
Authors: Schaal Christoph , Krautter Miriam , Hanss Michael 
Published: December 2012

AbstractIn order to localize cracks in cylindrical structures using guided waves, precise knowledge of the wave speeds is crucial. Instead of basing calculations on crisp parameters, for this Structural Health Monitoring application, uncertainty in parameters is handled by representing parameters as fuzzy numbers and applying the Transformation Method. For calculating dispersion curves, the Waveguide Finite Element Method is used for each parameter set. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Inter‐wire Coupling Model Development for Health Monitoring of Cable Structures
Authors: Higgins Natalie , Schaal Christoph 
Published: December 2012

AbstractStructural Health Monitoring (SHM) allows the integrity of a system to be monitored in situ, detecting weaknesses as they form. Due to the waveguide nature of cylindrical structures, ultrasonic waves can be used to detect defects in cables over large distances. Considering that common power line cables consist of several individual wires, a straightforward energy‐based approach is chosen to simplify the model development. The purpose of this investigation is to extend the current coupling model to include n wires and to verify this model for a seven‐wire cable, experimentally. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Study of Mode Conversion at Defects in Rope Structures using Ultrasonic Waves
Authors: Bischoff Stefan , Gaul Lothar 
Published: December 2012

AbstractUltrasonic waves travel in rope structures over long distances as guided waves, allowing for effective health monitoring. In order to localize and characterize defects, an exact knowledge of the propagation, reflection, and transmission properties of the ultrasonic waves is required. These properties can be obtained using the Finite Element Method by modeling a segment of the periodic waveguide with a periodicity condition. The solution of the corresponding eigenvalue problem leads to all propagating modes of the waveguide as well as locally generated evanescent modes. The Boundary Element Method (BEM) is used in combination with the Finite Element Method for characterizing the wave propagation. The mode conversion at discontinuities, such as cracks or notches, can be subsequently described by reflection and transmission coefficients. The simulation results are the corresponding coefficients as a function of frequency and enable the selection of adequate modes for an effective defect detection. Additionally, it is demonstrated that along with the localization of cracks, conclusions about the crack geometry can be made with the help of reflection and transmission coefficients. The reliability and numerical accuracy of the simulation results are verfied by comparison with experimental findings. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Microscale Investigations of Highfrequency Wave Propagation Through Highly Porous Media
Authors: Uribe David , Saenger Erik , Jänicke Ralf , Steeb Holger , Ruiz Oscar 
Published: December 2012

AbstractWave propagation in highly porous materials has a well established theoretical background. Still there are parameters which require complex laboratory experimentation in order to find numerical values. This paper presents an effective method to calculate the tortuosity of aluminum foam using numerical simulations. The work flow begins with the acquisition of the foam geometry by means of a micro‐CT scanner and further image segmentation and analysis. The elastodynamic wave propagation equation is solved using a velocity‐stress rotated staggered finite‐difference technique. The effective wave velocities are calculated and using the fluid and, aluminum effective properties, the tortuosity is determined. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)