bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of the intrinsic permeability of aluminium foam — Measurements and analytical calculation
Authors: Liebl Christoph , Lion Alexander 
Published: November 2010

AbstractA measuring system for the determination of the intrinsic permeability of highly porous materials is presented. The evaluation of the measurements is conducted on the basis of the Theory of Porous Media (TPM). By adjusting the calculation to the measurement results achieved with polyethylenglycol (PEG) 300 and open‐cell aluminium foam, the intrinsic permeability of the metal foam is determined. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Uniform Slip Flow on a Cylinder
Authors: Crane L. J. , McVeigh A. G. 
Published: November 2010

AbstractIn this paper, we determine the shear stress along the entire length of a stationary cylinder having radius a, under uniform axisymmetric flow, with velocity U0, in the slip regime. Investigating motion at small and large axial distances, we employ asymptotic series techniques to obtain the shear stress coefficient in non‐dimensional form. For intermediate regions, we obtain a solution using the Rayleigh approximation method. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Transonic viscous inviscid interactions in a slender Laval nozzle
Authors: Meyer Georg , Kluwick Alfred 
Published: November 2010

AbstractTransonic, high Reynolds number flows through a Laval nozzle, which is so narrow that the classical boundary layer correction can no longer be considered to be an effect of higher order, are considered. As a consequence the properties of the inviscid core and the viscosity dominated boundary layer region can no longer be determined in subsequent steps but have to be calculated simultaneously. The resulting interaction problem for laminar flows in a small nozzle is presented for perfect gases. Representative solutions including the internal structure of pseudo‐shocks forming in the diffuser part of the nozzle and being strongly associated with the chocking phenomenon will be presented. The linear stability of the various flow regimes observed in the nozzle will be discussed. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Two‐fluid spatial instability with velocity defect in the basic flow
Authors: Otto Thomas , Boeck Thomas , Rossi Maurice 
Published: November 2010

AbstractThe initial state of liquid atomization by a fast gas stream is considered by viscous linear spatial stability analysis for parallel two‐fluid flow. The unbounded basic velocity profile is characterized by boundary layers near the interface and different asymptotic velocities. By computing generalized spatial branches we identify conditions for absolute instability when a velocity deficit is introduced to account for the conditions near the nozzle. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A first Integral of Navier­Stokes equations for two‐dimensional flows
Authors: Scholle M. , Haas A. 
Published: November 2010

AbstractAs wellknown, Bernoulli's equation is obtained as the first integral of Euler's equations in the absence of vorticity. Even in case of non‐vanishing vorticity, a first integral from Euler's equations is obtained by using the so called Clebsch transformation [1] for inviscid flows. In contrast to this, a generalisation of this procedure towards viscous flows has not been established so far. In the present paper a first integral of Navier‐Stokes equations is constructed in the case of two‐dimensional flow by making use of an alternative representation of the fields in terms of complex coordinates and introducing a potential representation for the pressure. The associated boundary conditions are also considered. The first integral is a suitable tool for the development of new analytical methods and numerical codes in fluid dynamics. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Double Channel Membrane Pump
Authors: Steinrück Herbert , Zackl Wilhelm , Müllner Markus , Neth Harald 
Published: November 2010

AbstractThe flow through a double channel membrane pump is modeled by a time dependent potential flow. The total forces on the fluid are determined as a function of the position of the lateral pistons. It turns out that the total force and thus the pressure gain is very sensitive to the position of the excitation. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Diffraction of water waves by a slotted dual cylindrical caisson breakwater
Authors: Basmat A. 
Published: November 2010

AbstractThe linearized theory of water waves is used to examine the diffraction of incident regular waves by a slotted dual cylindrical caisson breakwater. The breakwater consists of a vertically slotted outer cylinder circumscribing an impermeable inner cylinder. Under the assumption that the wavelength is much greater than its thickness, each panel is replaced by a thin structure and the permeability is modeled by suitable boundary conditions applied on its surface. The mixed boundary‐value problem for the outer cylinder is transformed to dual series relations and the least‐square method is applied to get the forces on the structure and associated diffraction field. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experimental Evidence for Breather Type Dynamics in Freak Waves
Authors: Chabchoub Amin , Vitanov Nikolay , Hoffmann Norbert 
Published: November 2010

AbstractFreak or rogue waves on the ocean seemingly appear from nowhere, cause severe damage to ships and offshore structures due to their large crest heights, and disappear at once. Since the Draupner wave measured on New Year's day 1995 finally confirmed the existence of freak waves, different models were developed to describe them. One deterministic model to investigate their occurrence is the nonlinear Schrödinger equation (NLS) describing the nonlinear evolution of wave train envelopes. Due to the modulation instability, also referred to as Benjamin‐Feir instability, strong spatial localization of wave amplitude may arise and breather type solutions are hypothesized to form the dynamical back‐bone of rogue waves. To test this hypothesis, breather type solutions of the NLS are compared to two extreme wave records: the Draupner wave recorded in central North Sea and the Yura wave recorded in the Sea of Japan. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of Dispersion Characteristics of Composites
Authors: Karmazin Alexander , Kirillova Evgenia , Seemann Wolfgang , Syromyatnikov Pavel 
Published: November 2010

AbstractThis numerical study of dispersion characteristics of some symmetric and asymmetric composites modelled as multilayered packets of layers with arbitrary anisotropy of each layer is carried out. The authors introduce a subsidiary boundary problem of three‐dimensional theory of elasticity for the system of partial differential equations describing the harmonic oscillations of the composite excited by a surface load. The authors obtained the curves and surfaces describing slowness of the wave front of Lamb waves propagating with respect to the direction of propagation. The method suggested by the authors of the present article does not impose any restrictions on the type of elastic anisotropy of the layers, their orientations and mutual positions. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Transient wave propagation in a one dimensional partially saturated poroelastic column
Authors: Li Peng , Schanz Martin 
Published: November 2010

AbstractBased on the theory of mixtures, a dynamic three phase model for partially saturated poroelasticity is established. This model is applied to a one‐dimensional unsaturated poroelastic column and an analytical solution in the Laplace domain is deduced. By using the Convolution Quadrature Method, the solution in the time domain is obtained. Using some widely distributed porous materials as rock, soil and sediment, the wave propagation behavior in terms of displacement and pore pressure is examined. By neglecting the viscosity of the fluid, assuming very large fluid permeabilities, the second and third compressional waves are identified. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modal‐based fluid structure coupling in room acoustics considering non‐deterministic properties
Authors: Pospiech Martina , Buchschmid Martin , Rentrop Peter , Müller Gerhard 
Published: November 2010

AbstractNowadays fluid structure interaction methods gain more and more importance. For room acoustical problems the coupling to realistic boundary conditions, absorbers and reflectors, is still a remaining challenge in the optimization process for the frequency response of the acoustic volume. The following work will present a coupling method based on the Component Mode Synthesis and Hamilton's Principle for the steady state response of linear room acoustic problems. Therein realistic boundaries like absorbers are coupled with the help of their related frequency dependent impedances. For a more physical interpretation uncertain parameters are considered within the input data. Basic possibilistic and probabilistic concepts are applied on benchmark configurations to estimate the variation in frequency response functions from uncertain input data. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Wave‐Based Approach to Adaptively Control Self‐Excited Vibrations in Drill‐Strings
Authors: Kreuzer Edwin , Steidl Michael 
Published: November 2010

AbstractDue to their small diameter‐to‐length‐ratio, drill‐strings are vulnerable to torsional vibrations. Moreover, the string is exposed to unknown or uncertain time‐variant and nonlinear loads (e.g. friction with falling friction characteristics, contact with the borehole, differential sticking), which can result in severe torsional vibrations and stick‐slip. The control law for the boundary controller at the top drive of the string needs to adapt to those unknown loads in order to stabilize the vibrations. The torsional vibrations of a drill‐string are governed by the wave equation. Analytical solutions and control laws are often based on a separation of the dynamics into a time‐ and a space‐dependent part (modal representation). Here, we decompose the vibrations into two traveling waves according to the D'Alembert solution, using only few measurements along the string. The wave which travels up the string is then compensated by the actuator at the top drive. With this compensation, the upward‐traveling wave is no longer reflected back into the string and vibration energy is absorbed, thus stabilizing the torsional vibrations. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the Influence of Multi‐Layered Obstacles on the Wave Scattering Behaviour in TRC
Authors: Weber Wolfgang , Zastrau Bernd W. 
Published: November 2010

AbstractIn this contribution, the influence of the eccentricity of a multi‐layered scatterer to the wave scattering behaviour of Textile Reinforced Concrete is analyzed. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Eddy‐current braking of a translating solid bar by a magnetic dipole
Authors: Kirpo Maksims , Boeck Thomas , Thess Andrè 
Published: November 2010

AbstractThe paper addresses the problem of a conducting rectangular bar of square cross‐section which is moving with constant velocity in the field of an arbitrarily oriented magnetic dipole. The braking Lorentz force on the bar is obtained by FEM and compared with the analytical solution for a moving infinite plate in the field of a magnetic dipole [2]. The computation of the induced currents requires solution of a Laplace equation with mixed boundary conditions for the electric potential inside the moving bar. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An inhomogeneous, anisotropic, elastically modified Gibbs­Thomson law as singular limit of a diffuse interface model
Authors: Kraus Christiane , Garcke Harald 
Published: November 2010

AbstractWe consider the sharp interface limit of a diffuse phase‐field model with prescribed total mass taking into account a spatially inhomogeneous, anisotropic interfacial energy and an elastic energy. The main aim is to establish a weak formulation of an inhomogeneous, anisotropic, elastically modified Gibbs‐Thomson law in the sharp interface limit. To this end we pass to the limit in the weak formulation of the Euler‐Lagrange equation of the diffuse phase‐field energy. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
1D wave propagation in a rod: analytic treatment for non‐trivial boundary conditions
Authors: Schwarz Cornelia , Werner Ewald , Dirschmid H.J. 
Published: November 2010

AbstractAn analytic solution method for the one‐dimensional wave propagation problem in a rod based on the Laplace transform is applied to a simple stamping model. While the rod is mounted at its lower end to a spring, it is hit at its upper end by an impacting mass, the separation of which can be correctly treated by the method. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multiscale Simulation of the mechanical properties and the structural dynamics of a copper foam
Authors: Schwarzer Daniel , Proppe Carsten 
Published: November 2010

AbstractIn this contribution, a simulation chain for the prediction of the structural dynamics behavior of metal foam is proposed: Starting with investigations of the mesoscopic structure and topology, the linear elastic material properties and their scatter are computed with the help of mesoscopic non‐representative volume elements. Also their probability functions are estimated. In order to be able to describe the mechanical properties as random fields, the autocorrelation function and the power spectral density are determined.The next step in the proposed simulation chain is to generate realisations of the random fields with the help of the Karhunen‐Loeve expansion or the Spectral Representation. Afterwards, these realisations are used in Monte‐Carlo‐Simulations on the macroscale in order to predict the eigenfrequencies of beams and their scatter.With this multiscale approach, the mechanical properties of an open‐celled Copper foam are determined by simulations and the eigenfrequencies are compared to experimental results. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Evolutionary Iterative Optimum‐Optimorum Theory with Aerospace Applications
Authors: Nastase Adriana 
Published: November 2010

AbstractIn this paper, the author tries to improve the accuracy of the start solutions for the aerodynamical global optimization of the FC shapes by replacing the three‐dimensional, analytical hyperbolical potential solutions with new own developed hybrid numerical solutions for the Navier‐Stokes layer (NSL). These solutions have also analytical properties and are split. It follows a more rapid convergence and, consequently, a speed up of the computation time. The evolutionary iterative optimum‐optimorum theory uses these hybrid solutions after the first step of iteration and easy allows the weak interactions with the structure, via new and/or modified initial constraints, requested for the structure point of view. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimal Open‐Loop Feedback Control of Robots under uncertainty
Authors: Schacher Michael 
Published: November 2010

AbstractThe aim of this presentation is to construct an optimal open‐loop feedback controller for robots, which takes into account stochastic uncertainties. This way, optimal regulators being insensitive with respect to random parameter variations can be obtained.Usually, a precomputed feedback control is based on exactly known or estimated model parameters. However, in practice, often exact informations about model parameters, e.g. the payload mass, are not given. Supposing now that the probability distribution of the random parameter variation is known, in the following, stochastic optimisation methods will be applied in order to obtain robust open‐loop feedback control.Taking into account stochastic parameter variations, the method works with expected cost functions evaluating the primary control expenses and the tracking error. The expectation of the total costs has then to be minimized. Corresponding to Model Predictive Control (MPC), here a sliding horizon is considered. This means that, instead of minimizing an integral from a starting time point t0 to the final time tf, the future time range [t; t+T], with a small enough positive time unit T, will be taken into account. The resulting optimal regulator problem under stochastic uncertainty will be solved by using the Hamiltonian of the problem. After the computation of a H‐minimal control, the related stochastic two‐point boundary value problem is then solved in order to find a robust optimal open‐loop feedback control.The performance of the method will be demonstrated by a numerical example, which will be the control of robot under random variations of the payload mass. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimal design and sensitivity of large scale plane frames for the case of uncertainty
Authors: Zier Simone 
Published: November 2010

AbstractThis paper deals with the optimal design and the robustness of large scale plane frames in dependence of their height. Using the first collapse theorem, the necessary and sufficient survival conditions of an elasto‐plastic structure consist of the yield condition and the equilibrium condition. The basis for our consideration is provided by a plane n‐storey frame which will be increased successively, and which is affected by applied random forces and moments. Taking into account these random applied loads, we get a stochastic structural optimization problem which cannot be solved using the traditional methods. Instead of that, an appropriate (deterministic) substitute problem is formulated. First, the recourse problem will be formulated in general and in the standard form of stochastic linear programming (SLP), and after the formulation of the stochastic optimization problem, the Recourse Problem based on Discretization (RPD) is introduced as a representative of substitute problems. The resulting (large scale) linear program (LP) can be solved efficiently by means of usual LP‐solvers. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Error bounds for non‐selfadjoint PDE eigenvalue problems
Authors: Mehrmann Volker , Międlar Agnieszka 
Published: November 2010

AbstractWe introduce a posteriori bounds for the eigenfunctions (eigenvalues) of non‐selfadjoint diagonalizable PDE‐eigenvalue problems which incorporates an inexact solution of the corresponding generalized matrix eigenvalue problem. The estimates combine the standard perturbation results with the saturation assumption for the eigenfunctions. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the Convergence Theory of Preconditioned Subspace Iterations for Eigenvalue Problems
Authors: Zhou Ming 
Published: November 2010

AbstractWe consider preconditioned subspace iterations for the numerical solution of discretized elliptic eigenvalue problems. For these iterative solvers, the convergence theory is still an incomplete puzzle. We generalize some results from the classical convergence theory of inverse subspace iterations, as given by Parlett, and some recent results on the convergence of preconditioned vector iterations. To this end, we use a geometric cone representation and prove some new trigonometric inequalities for subspace angles and canonical angles. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Choosing norms in adaptive FSI calculations
Authors: Birken Philipp , Quint Karsten , Hartmann Stefan , Meister Andreas 
Published: November 2010

AbstractThe thermal coupling of a fluid and a structure is of great significance for many industrial processes. As a model for cooling processes in heat treatment of steel we consider the coupling of the compressible Navier‐Stokes equations along a surface with the heat equation. A partitioned approach is considered, where different codes for the sub‐problems are employed. We use a finite volume method (FVM) for the fluid and a finite element method (FEM) for the heat equation.The semi‐discrete coupled system is solved using stiffly stable SDIRK methods, where on each stage an FSI problem is solved. This has a black box character, since a stage calculation corresponds to a specific Backward‐Euler integration step. For the resulting method it was shown by numerical experiments in [1] that second order convergence rate is obtained. This property is used for a simple time‐step control, which saves considerable computational time and guarantees a specified maximum error of time integration. Here, we will consider different norms for measuring the error. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Weakly Singular Collocation Boundary Element Formulation for Linear Poroelasticity
Authors: Messner M. , Schanz M. 
Published: November 2010

AbstractOne major problem when discretizing boundary integral equations are the spatial singularities of the appearing integral kernels. For some classical problems, e.g. elastodynamics, this problem has been solved through partial integration yielding at most weakly singular integrals. The aim is to adopt this procedure to the modelling of porous media with boundary elements. This idea is justified by the fact that in saturated linear poroelasticity, Biot's theory couples a linear elastic solid with an acoustic fluid. Therefore, the reduction of the singularities can be achieved by the same techniques as for those problems. Due to the use of the convolution quadrature method, which permits a time domain discretization of boundary integral equations based on the Laplace domain fundamental solution, this is done in Laplace domain. For domains with closed surfaces, a weakly singular representation of the first boundary integral equation is presented. This equation is used for a collocation boundary element formulation involving only the numerical evaluation of weakly singular integrals. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical analysis for phase field simulations of moving interfaces with topological changes
Authors: Bartels Sören , Müller Rüdiger 
Published: November 2010

AbstractPhase field methods are a widely accepted tool for the approximation of moving free interfaces in sharp interface problems. Topological changes in the solution, such as nucleation or vanishing of particles or merging or pinching of interfaces, lead to singularities in the free boundary. In the sharp interface model, these singularities cause both numerical and theoretical problems, whereas they are handled “automatically” in phase field simulations. Phase field models contain a length scale ε > 0 that vanishes in the sharp interface limit. Therefore, when ε → 0, practical numerical methods have to be robust in the sense that error estimates may only depend polynomially on ε‐1, not exponentially. We show that robust error control is possible past the occurrence of topological changes and without restrictive assumptions on the initial data. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Parallelization of the time integration for time‐periodic flow problems
Authors: Obrist Dominik , Henniger Rolf , Arbenz Peter 
Published: November 2010

AbstractThe solution of a time‐periodic flow problem is expanded into a discrete Fourier series. This yields a large nonlinear system of equations which can be solved in parallel. We show for a one‐dimensional model problem that this method for the parallelization of the time domain converges in a robust and efficient manner. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)