bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental investigation of a flexible high‐water protection system in a down‐scale water channel flow
Authors: Schade Klaus‐Peter , Sommer Oliver , Wozniak Günter 
Published: October 2016

AbstractAs part of an interdisciplinary major project regarding the development of a flexible and efficiently installable high‐water protective system we investigated the behaviour of different system parts of flexible channel walls (thin, plastic slides/membranes) and types of self‐installing water barricades subjected to different water channel flows experimentally and numerically. In the experiments we studied the strain of different flexible channel walls and the efficiency of various water barricades in a down‐scale model by optical deformation, flow velocity and time measurements, respectively. We varied the water height as well as the representative flow velocity of the water channel flow and we also examined the influence of water waves onto these high‐water protective system parts. Selected results will be shown and described concerning the stress on the used model‐slide. In addition we applied similarity theory not only for general data presentation but also to generate findings regarding a future practical implementation in technical applications. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Wall‐cooling effect on linear stability of compressible streamwise corner‐flow
Authors: Staudenmeyer Jennifer , Rist Ulrich 
Published: October 2016

AbstractThe influence of constant wall temperatures on the compressible flow along a right‐angled corner and its stability behaviour is investigated by temporal local linear stability analysis. Wall‐cooling up to 90 % of the adiabatic wall‐temperature for a subsonic flow (Ma = 0.95) is considered. The maximum cross‐flow velocity along the corner bi‐sector for the base flow with adiabatic wall boundary condition is higher than for the base flow with constant adabatic wall‐temperature. For increasing wall temperature, the amplification rate of the viscous modes decreases to a lesser extent than that of the corner mode, therefore the critical Reynolds‐number is further on defined by the first viscous mode. The spatial behaviour is displayed using N‐factors computed from Gaster‐transformed modes. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Enhanced and reduced natural convection using magnetic fluid in a square cavity
Authors: Szabo Peter S. B. , Früh Wolf‐Gerrit 
Published: October 2016

AbstractNatural convection using a magnetic fluid was studied in a square cavity under the influence of a permanent magnet. The aim was to explore the degree by which heat transfer may be controlled, enhanced or reduced, by investigating a set of different distances of a permanent magnet to the cavity. These distances of the magnet were set such that the cavity was in some cases fully dominated by buoyancy or by the magnetic body force and in other cases partly dominated by either of both body forces in different parts of the fluid. The effect on heat transfer was characterised by an averaged Nusselt number, Rayleigh and magnetic Rayleigh number. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An entropic gradient structure for quasi‐steady‐state approximations of chemical reactions
Authors: Disser Karoline 
Published: October 2016

AbstractPassing to the limit of an infinite reaction rate in a slow‐fast system of chemical reactions provides a quasi‐steady state approximation (QSSA) of these systems. In case of reactions with detailed balance condition, this approximation includes a dimension reduction to a smaller state space. We show that the limit dynamics carry an entropic gradient structure on this smaller space. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Rank‐one convexity implies polyconvexity for isotropic, objective and isochoric elastic energies in the two‐dimensional case
Authors: Martin Robert J. , Neff Patrizio , Ghiba Ionel‐Dumitrel 
Published: October 2016

AbstractWe show that in the two‐dimensional case, every objective, isotropic and isochoric energy function which is rank‐one convex on GL+(2) is already polyconvex on GL+(2). Thus we negatively answer Morrey's conjecture in the subclass of isochoric nonlinear energies, since polyconvexity implies quasiconvexity. Our methods are based on different representation formulae for objective and isotropic functions in general as well as for isochoric functions in particular. We also state criteria for these convexity conditions in terms of the deviatoric part of the logarithmic strain tensor. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Geometric uncertainties in finite element models of mistuned bladed disks
Authors: Koebelé‐Cousquer Maxime , Proppe Carsten 
Published: October 2016

AbstractThis paper presents a method to develop reduced‐order models of bladed disks with geometric mistuning, which is based on polynomial choas approximation of modes of random eigenvalue subproblems. This method allows to reduce mass and stiffness matrices without evaluating the deviation in these matrices due to mistuning. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Input‐output behaviour of a stochastic Galerkin method for a low pass filter
Authors: Pulch Roland 
Published: October 2016

AbstractWe apply the stochastic Galerkin method to a linear dynamical system, which includes random variables to quantify uncertainties in physical parameters. The input‐output behaviour of the stochastic Galerkin system is described by a transfer function in the frequency domain. The importance of each output component can be estimated by Hardy norms. We investigate a Hardy norm in the case of a linear dynamical system modelling the electric circuit of a low pass filter. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bat algorithm for optimization of reinforced concrete columns
Authors: Bekdas Gebrail , Nigdeli Sinan Melih 
Published: October 2016

AbstractIn structural mechanics, when the design contains two different materials with opposite mechanical behaviours and costs, the optimum design cannot exactly found. In that case, numerical optimization algorithms are a good source. Reinforced concrete design shows that behaviour since concrete is a cheap material comparing to steel while the tensile strength of concrete is very low to use. The cross sections are effective on the stresses and balance of tensile and compressive forces. This situation shows the importance of the dimension optimization of reinforced concrete members. Also, the number and size of the reinforcements need an optimization. The place of the reinforcements is effective on the place of tensile forces in the calculation of axial force and flexural moment capacity. In this paper, reinforced concrete columns are optimized for the cost minimization by employing a bio‐inspired metaheuristic algorithm called bat algorithm. The idealization of the echolocation behaviour of bats is the inspiration of the bat algorithm. Differently from the algorithms, the bat algorithm uses global and local optimization with a changeable probability. The optimization process considers the security measures and slenderness of the according to the design regulation called ACI 318. The slenderness is taken into consideration by using a magnified design flexural moment, which is factored by a value defined according to the buckling load and axial load of columns. The proposed approach is applied for different numerical cases and the results are compared with the approach using harmony search algorithm. The present approach is effective for the optimization problem. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Step‐size Adaptation in a Multi‐objective Differential Evolution Algorithm
Authors: Boblenz Christian , Bestle Dieter 
Published: October 2016

AbstractIf Differential Evolution (DE) is applied to multi‐objective optimization problems, some of its features like automatic problem‐specific step‐size adaptation gets lost. This can be resolved by modifying the DE equations. Three strategies are proposed and compared with existing algorithms. It is shown, that the proposed strategies deliver a superior convergence and preserve the positive characteristics of DE known from solving mono‐objective optimization problems. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An extended cost estimation model for a multi‐material topology optimization approach
Authors: Falkenberg Paul , Vietor Thomas 
Published: October 2016

AbstractThe manufacturing costs of hybrid parts comprise several different proportions depending on the manufacturing process and the materials used. A simplified cost model based on the material weights is therefore no longer sufficient.In this paper, an approach for the weight and costs optimization of hybrid parts is presented. An extended costs calculation function regarding additional manufacturing costs and the integration of a new cost objective in the optimization process is investigated. The effects of the consideration of costs on the optimization results will be qualitatively shown on a simple example structure. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A modified metaheuristic optimization approach on the structural identification and damage detection of an experimentally tested wind turbine supporting structure
Authors: Jahjouh Mahmoud , Nackenhorst Udo 
Published: October 2016

AbstractWind energy conversion devices (WECDs) are sensitive structures subjected to high force fluctuations, making them prone to damage. Thus, a global identification and damage detection technique is important to keep track of any changes in the structural characteristics of the WECD.In this contribution, a previously‐developed structural identification and damage detection algorithm, namely: the Modified Adaptive HaRmony SearcH ALgorithm (MARSHAL), is used to perform structural identification and damage detection to a laboratory test model of a WECD supported by a tripile. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An evolution equation based approach to topology optimization
Authors: Jantos Dustin Roman , Junker Philipp , Hackl Klaus 
Published: October 2016

AbstractThe objective of topology optimization is to find a mechanical structure with maximum stiffness and minimal amount of used material for given boundary conditions [2]. There are different approaches. Either the structure mass is held constant and the structure stiffness is increased or the amount of used material is constantly reduced while specific conditions are fulfilled. In contrast, we focus on the growth of a optimal structure from a void model space and solve this problem by introducing a variational problem considering the spatial distribution of structure mass (or density field) as variable [3]. By minimizing the Gibbs free energy according to Hamilton's principle in dynamics for dissipative processes, we are able to find an evolution equation for the internal variable describing the density field. Hence, our approach belongs to the growth strategies used for topology optimization. We introduce a Lagrange multiplier to control the total mass within the model space [1]. Thus, the numerical solution can be provided in a single finite element environment as known from material modeling. A regularization with a discontinuous Galerkin approach for the density field enables us to suppress the well‐known checkerboarding phenomena while evaluating the evolution equation within each finite element separately [4]. Therefore, the density field is no additional field unknown but a Gauß‐point quantity and the calculation effort is strongly reduced. Finally, we present solutions of optimized structures for different boundary problems. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Robust Damping in Self‐Excited Mechanical Systems
Authors: Jekel Dominic , Clerkin Eoin , Hagedorn Peter 
Published: October 2016

AbstractA technique to optimize the stability of a general mechanical system is outlined. The method relies on decomposing the damping matrix into several component matrices, which may have some special structure or physical relevance. An optimization problem can then be formulated where the ratio of these are varied to either stabilize or make more stable the equilibrium state subject to sensible constraints. For the purpose of this study, we define a system to be more stable if its eigenvalue with largest real part is as negative as possible. The technique is demonstrated by applying it to an introduced non‐dimensionalized variant of a known minimal wobbling disc brake model. In this case, it is shown to be beneficial to shift some damping from the disc to the pins for a system optimized for stability. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimisation of Structures with Inelastic Deformations
Authors: Liedmann Jan , Barthold Franz‐Joseph 
Published: October 2016

AbstractIn context of design optimisation, the treatment of inelastic, path‐dependent materials is a topic of interest. As opposed to purely elastic materials, it is necessary to store and analyse the deformation history in order to appropriately describe inelastic material behaviour. For design optimisation of structures sensitivities of all quantities of influence have to be computed so as to use gradient based optimisation algorithms. Considering path‐dependent materials the sensitivities of internal variables that represent the deformation history have to be additionally calculated. A numerical effective way of determining sensitivities is the variational sensitivity analysis. This approach is applied to develop a powerful and effective algorithm to compute sensitivities of the structural response with respect to their geometric design. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Global Optimization of the Shape of a Suborbital Space Vehicle
Authors: Nastase Adriana 
Published: October 2016

AbstractThe determination of the global optimized (GO) shapes of flying configurations leads to extended variational problems with free boundaries. The author has developed special optimization strategies called optimum optimorum and iterative optimum optimorum strategies and have used them for the design of GO shapes of three models, which are of minimum drag at three different supersonic cruising Mach numbers. These optimization strategies can be used for the determination of new GO shapes of more performant supersonic transport aircraft and space vehicles. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structural design sensitivity analysis in context of non‐linear buckling
Authors: Radau Lukas , Gerzen Nikolai , Barthold Franz‐Joseph 
Published: October 2016

AbstractStructural stability is an important issue to ensure the safety of thin walled structures. Shell structures are considered in context of linear and non‐linear buckling. The design sensitivity analysis with respect to modifications in shape is motivated. Analytically derived gradient information is employed for shape optimisation purposes using solid shells. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Combined Newton‐Kurchatov method for solving nonlinear operator equations
Authors: Iakymchuk Roman , Shakhno Stepan , Yarmola Halyna 
Published: October 2016

AbstractWe investigate local and semi‐local convergence of the combined Newton‐Kurchatov method under the classical and generalized Lipschitz conditions for solving nonlinear equations. The convergence order of the method is examined and the uniqueness ball for the solution of the nonlinear equation is proved. Numerical experiments are conducted on test problems. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A note on terminology in multigrid methods
Authors: Birken Philipp , Bull Jonathan , Jameson Antony 
Published: October 2016

AbstractWe compare terminology used in the literature on multigrid methods for compressible computational fluid dynamics to that used in linear multigrid theory. Several popular iterative and direct smoothers are presented side‐by‐side using the same terminology. We argue for greater analysis of these methods in order to place them into a more rigorous framework and to identify the most promising candidates for future development. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical solution to low rank perturbed Lyapunov equations by the sign function method
Authors: Benner Peter , Denißen Jonas 
Published: October 2016

AbstractWe investigate the numerical solution to a low rank perturbed Lyapunov equation
ATX + XA = W
via the sign function method (SFM). The sign function method has been proposed to solve Lyapunov equations, see e.g. [1], but here we focus on a framework where the matrix A has a special structure, i. e.
A = B + UCVT,
where B is a blockdiagonal matrix and UCVT is a low rank perturbation. We show that this structure can be kept throughout the sign function iteration but the rank of the perturbation doubles per iteration. Therefore, we apply a low rank approximation to the perturbation in order to keep its numerical rank small. We compare the standard SFM with its structure preserving variant presented in this paper by means of numerical examples from viscously damped mechanical systems. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Connection between Time Domain Model Order Reduction and Moment Matching
Authors: Hund Manuela , Saak Jens 
Published: October 2016

AbstractWe investigate the time domain model order reduction (MOR) framework using general orthogonal polynomials by Jiang and Chen [4] and extend their idea by exploiting the structure of the corresponding linear system of equations. Identifying an equivalent Sylvester equation we show a connection to a rational Krylov subspace, and thus moment matching. This theoretical link between the MOR techniques is illustrated by one numerical example. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Convergence Analysis of the Dirichlet‐Neumann Iteration for Finite Element Discretizations
Authors: Monge Azahar , Birken Philipp 
Published: October 2016

AbstractWe analyze the convergence rate of the Dirichlet‐Neumann iteration for the fully discretized unsteady transmission problem. Specifically, we consider the coupling of two linear heat equations on two identical non overlapping domains with jumps in the material coefficients across these. In this context, we derive the iteration matrix of the coupled problem. In the 1D case, the spectral radius of the iteration matrix tends to the ratio of heat conductivities in the semidiscrete spatial limit, but to the ratio of the products of density and specific heat capacity in the semidiscrete temporal one. This explains the fast convergence previously observed for cases with strong jumps in the material coefficients. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On isotropy conditions in second gradient materials
Authors: Münch Ingo , Neff Patrizio 
Published: October 2016

AbstractIn gradient elasticity, isotropy and frame‐indifference requirements are sensitive to the homogeneity of the applied rotation field Q ∈ SO(3). This is in contrast to standard elasticity, where only first gradients of the deformation are under consideration. We use a diffeomorphism to show the effect of inhomogeneous coordinate transformation to the form‐invariance requirement of elastic energy. From a classical geometric rigidity result follows that the appearance of a right‐local SO(3)‐invariance condition is not the general condition for isotropy. The correct statement for isotropy in second gradient elasticity should be a right‐global SO(3)‐invariance condition. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fast interior point solvers for H1‐regularized PDE‐constrained optimization problems
Authors: Pearson John W. , Gondzio Jacek 
Published: October 2016

AbstractWe consider Newton systems arising from the interior point solution of PDE‐constrained optimization problems. In particular, we examine problems where the control variable is regularized by an H1‐norm within the cost functional. We present preconditioned iterative methods for the resulting matrix systems, and justify the potency of our approach through numerical experiments. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Towards adaptive discontinuous Petrov‐Galerkin methods
Authors: Bringmann P. , Carstensen C. , Gallistl D. , Hellwig F. , Peterseim D. , Puttkammer S. , Rabus H. , Storn J. 
Published: October 2016

AbstractThe discontinuous Petrov‐Galerkin (dPG) method is a minimum residual method with broken test functions for instant stability. The methodology is written in an abstract framework with product spaces. It is applied to the Poisson model problem, the Stokes equation, and linear elasticity with low‐order discretizations. The computable residuum leads to guaranteed error bounds and motivates adaptive refinements. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multiscale Petrov‐Galerkin FEM for Acoustic Scattering
Authors: Gallistl Dietmar , Peterseim Daniel , Carstensen Carsten 
Published: October 2016

AbstractWe present a pollution‐free Petrov‐Galerkin multiscale finite element method for the Helmholtz problem with large wave number κ. We use standard continuous Q1 finite elements at a coarse discretization scale H as trial functions. The test functions are the solutions of local problems at a finer scale h. The diameter of the support of the test functions behaves like mH for some oversampling parameter m. Provided m is of the order of log(κ) and h is sufficiently small, the resulting method is stable and quasi‐optimal in the regime where H is proportional to κ−1. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Uncertainty Quantification for Two‐Phase Flow in Heterogeneous Porous Media
Authors: Köppel Markus , Rohde Christian 
Published: October 2016

AbstractThe simulation of flow and transport in porous media such as aquifers often involve dealing with complex heterogeneities. They are characterized by varying hydrogeological properties which differ strongly from the adjacent medium and often lead to significant changes of the flow behavior. However detailed information about the location of such heterogeneities is not always known. The deterministic models thus need to be extended stochastically to quantify uncertainties. As mathematical model we use the capillarity‐free fractional flow formulation for two immiscible and incompressible fluid phases in a two‐dimensional and partitioned domain. To cope with the randomly located heterogeneity interfaces we employ a stochastic Galerkin (SG) method [4]. The physical space of this system then is modelled by a central upwind finite volume scheme [5] in combination with mixed finite elements [7]. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Variational integrators of higher order for constrained dynamical systems
Authors: Wenger Theresa , Ober‐Blöbaum Sina , Leyendecker Sigrid 
Published: October 2016

AbstractThe variational integrators presented in [5] are applied to systems with holonomic constraints, yielding constrained higher order variational integrators that are an extension of the constrained Galerkin methods in [4]. The construction of the integrators bases on a discrete version of Hamilton's principle. The inheritance of qualitative properties associated to the solution of the dynamical system to the discrete solution is analysed. Furthermore, the convergence order of the integrators and the computational efficiency is investigated numerically. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)