bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reduction of fuel consumption of small gas turbines at idling under combined operation with adjustable compressor inlet and turbine outlet guide vanes
Authors: Borchert Uwe 
Published: November 2019

AbstractFor the experimental verification of the effect of adjustable compressor inlet guide vanes combined with adjustable turbine outlet guide vanes for reducing the fuel consumption at idling, an 8 kW test gas turbine was designed and built up. The data of the experiments with the test gas turbine was compared with experimental data acquired by the author from another gas turbine. Additionally, experimental data was compared with external data of other heat engines. Using the newly introduced dimensionless Kruschik number, the test gas turbine, two series gas turbines and an internal combustion engine was compared in terms of their required heat supply at idling.
Dynamic selection limiter schemes for high density gradient simulations of supersonic rarefied gas flows
Authors: Groll Rodion 
Published: November 2019

AbstractFor modelling thrust and efficiency of micro propulsion sytems standard DSMC methods with static collision limiter schemes do not differentiate between regions with varying degrees of flow rarefaction and different DSMC particle densities. The discrete influence of multi‐level grid coarsening and different elongations of the numerical time step on the quality of predicted flow quantities show the advateges of the dynamic collision limitation.
Lagrangian perspectives on turbulent superstructures in Rayleigh‐Bénard convection
Authors: Klünker Anna , Schneide Christiane , Pandey Ambrish , Padberg-Gehle Kathrin , Schumacher Jörg 
Published: November 2019

AbstractWe analyze large‐scale patterns in three‐dimensional turbulent convection in a horizontally extended square convection cell by means of Lagrangian particle trajectories calculated in direct numerical simulations. Different Lagrangian computational methods, i.e. finite‐time Lyapunov exponents, spectral and density‐based clustering and transfer operator approaches, are used to detect these large‐scale structures, which are denoted as turbulent superstructures of convection.
A‐priori pole selection for reduced models in vibro‐acoustics
Authors: Aumann Quirin , Müller Gerhard 
Published: November 2019

AbstractLarge models of complex dynamic systems can be evaluated efficiently using model order reduction methods. Many techniques, for example the iterative rational Krylov algorithm (IRKA), rely on a set of expansion points chosen before the reduction procedure. The number and location of the expansion points has a major impact on the quality of the resulting reduced model and the convergence of the algorithm. Based on the system's geometry and material, the number of modes in a certain frequency range can be computed using wave equations. This mode count allows the choice of both a reasonable size for the reduced model as well as a reasonable distribution of initial expansion points, which improves the convergence of IRKA. Using the mode count in a specific frequency range, a reduced model approximating the full model only in this frequency range can be generated.
Drag Reduction of Transversal Surface Waves with Sweep Angle
Authors: Meysonnat Pascal S. , Albers Marian , Schröder Wolfgang 
Published: November 2019

AbstractLarge‐eddy simulations of oblique spanwise traveling transversal surface waves in turbulent boundary layer flow are conducted. The results show a minor dependence of the drag reduction on the wave angle for small angles and downstream traveling waves and a strong decrease of the drag for upstream traveling waves.
On the nullity of homogeneous linearized kinematic and equilibrium equations of a system of supported and connected rigid bodies
Authors: Flajs Rado 
Published: November 2019

AbstractThis paper deals with homogeneous linearized kinematic equations and the equilibrium equations of systems of supported and connected rigid bodies, the type of which were encountered during the undergraduate course of Statics within the first year of the study of Civil Engineering at the University of Ljubljana. In the paper the very fundamental relationnullity(A) = nullity(BT)is proven using the well‐known virtual work principle. Here, matrices A and B denote the matrix of the homogeneous linearized kinematic equations and the matrix of the equilibrium equations, respectively. Since the well‐known equilibrium equations

could potentially lack a physical interpretation [1], a new proof for a smaller set of the equilibrium equations, preferable in practical and pedagogical sense [2,3], is presented.
Computational study of ventricular fibrillation by considering a strongly coupled electromechanical rat heart model
Authors: Holz David , Duong Minh Tuan , Alkassar Muhannad , Dittrich Sven , Leyendecker Sigrid 
Published: November 2019

AbstractFully coupled electromechanical models of the heart have demonstrated the importance of computational models to better understand the cause, evolution and termination of ventricular fibrillation (VF). Especially these kinds of models are used to study the interplay between the mechanoelectrical feedback (MEF) and VF. In this study, we investigate the influence of the MEF in a strongly coupled excitation‐contraction model on the VF behaviour of a MRI based rat left ventricle (LV) by varying the maximum conductance of the stretch activated channels (SACs). We finally compare the action potential (AP) evolution and apex displacement under different strengths of the MEF.
Coherent vortex structure investigation behind the axial fan in pipe
Authors: Čantrak Ðorđe , Janković Novica , Nedeljković Miloš 
Published: November 2019

AbstractExperimental investigation of the coherent vortex structure in pipe on the axial fan pressure side, by use of the velocity optical measurement techniques, is reported in this paper. Generated vortex structure, its velocity and turbulent statistical values are revealed and discussed.
Simulating plant‐cell dehydration using a double‐porosity formulation based on the Theory of Porous Media
Authors: Eurich Lukas , Shahmoradi Shahla , Wagner Arndt , Borja Ronaldo , Ehlers Wolfgang 
Published: November 2019

AbstractMany living organisms, particularly plant tissues, exhibit very interesting features with regard to technical applications. For example, many plant tissues are frost resistant, which is mainly due to the dehydration of their tissue cells as one of the crucial mechanisms to cope with subzero temperatures. In this contribution, a fully coupled thermo‐hydro‐mechanical model based on the Theory of Porous Media is applied to assess the impact of ice formation on the water content of the tissue cells. Special attention is paid to the water exchange from the cells to the macro‐pore space.
Elasticity suppresses viscous fingering in a reactive Hele‐Shaw cell
Authors: Mokbel Dominic , Aland Sebastian 
Published: November 2019

AbstractWe consider a system of two liquids in a Hele‐Shaw cell that form a viscoelastic material layer between them by a chemical reaction. Is has been demonstrated that this system leads to a fingering instability, supposedly by the elasticity of the newly created material phase. To explore this mechanism we employ a novel phase‐field model [1], which can handle fluid‐structure interaction involving growing elastic materials. Assuming the newly created phase to be a viscoelastic Kelvin‐Voigt material, we find that this mechanism alone does not explain the experimentally observed fingering. Imposing a viscosity contrast between the materials, we even find the presence of elasticity to suppress any viscous fingering.
Multigrid‐reduction‐in‐time for Eddy Current problems
Authors: Friedhoff Stephanie , Hahne Jens , Schöps Sebastian 
Published: November 2019

AbstractParallel‐in‐time methods have shown success for reducing the simulation time of many time‐dependent problems. Here, we consider applying the multigrid‐reduction‐in‐time (MGRIT) algorithm to a voltage‐driven eddy current model problem.
Artificial intelligence control applied to drag reduction of the fluidic pinball
Authors: Cornejo Maceda Guy Y. , Noack Bernd R. , Lusseyran François , Deng Nan , Pastur Luc , Morzynski Marek 
Published: November 2019

AbstractThe aim of our work is to advance a self‐learning, model‐free control method to tame complex nonlinear flows—building on the pioneering work of Dracopoulous [1]. The cornerstone is the formulation of the control problem as a function optimization problem. The control law is derived by solving a nonsmooth optimization problem thanks to an artificial intelligence technique, genetic programming (GP). Metaparameters optimization of the algorithm and complexity penalization have been our main contribution and have been tested on a cluster of three equidistant cylinders immersed in a incoming flow, the fluidic pinball. The means of control is the independent rotation of the cylinders. GP derived a control law associated to each cylinder in order to minimize the net drag power and managed to outperform past open‐loop studies with a 46.0 % net drag power reduction by combining two strategies from literature. This success of MIMO control including sensor history is promising for exploring even more complex dynamics.
An Artificial Neural Network based Solution Scheme to periodic Homogenization
Authors: Göküzüm Felix Selim , Nguyen Lu Trong Khiem , Keip Marc-André 
Published: November 2019

AbstractArtificial neural networks (ANNs) have aroused research's and industry's interest due to their excellent approximation properties and are broadly used nowadays in the field of machine learning. In the present contribution, ANNs are used for finding solutions of periodic homogenization problems. The construction of ANN‐based trial functions that satisfy the given boundary conditions on the microscale allows for the unconstrained optimization of a global energy potential. Goal of the present approach is a memory efficient solution scheme as ANNs are known to fit complicated functions with a relatively small number of internal parameters. The method is tested for a three‐dimensional example using a global trial function and is qualitatively compared to a fast Fourier transform (FFT) based simulation.
Non‐linear vibrations in rotor systems with floating ring bearings induced by fluid‐structure interactions
Authors: Woschke Elmar , Nitzschke Steffen , Daniel Christian 
Published: November 2019

AbstractAlthough the use of combustion engines will decrease in passenger cars due to ecological reasons, turbochargers (TC) as typical applications with floating ring bearings will furthermore be applied in other applications like combined heat and power plants, ships or emergency backup generators for data processing service center and similar systems. Thus, the development of TC concerning rotor‐ and hydrodynamics is an important task, which leads due to the non‐linear behaviour to the necessity of advanced simulations for improving the performance.
Geometric a‐priori evaluation of sample designs
Authors: Daum Rebecca 
Published: November 2019

AbstractHighly complex FEM models for crash simulations require large computing capacities. A meaningful sample design is crucial for applications with large sensitivities. Latin Hypercube sampling techniques allow for a flexible number of sample points without specifying the required number of sample points for specific applications. We present an a‐priori technique for evaluating sample designs for highly sensitive applications.
A geometric nonlinear model for rotating cylindrical shells
Authors: Schmidt Rico , Ams Alfons 
Published: November 2019

AbstractShell structures are extensively used in engineering for constructions with light weight and high strength. Classical applications are covers in automotive industry, aero‐ and astronautics. For this purpose the dynamical behaviour is of interest for safety and comfort. The focus will be placed on rotating circumferential cylindrical shells.Starting with the geometrical nonlinear kinematics for the strains, the HAMILTON's principle is evaluated. In the following‐up to the calculus of variation RITZ approach is used, to compute eigenfrequencies. Afterwards the results are discussed for certain examples and compared to FE‐solutions.
Modal Flatness Analysis of Thin Sheets
Authors: Gruber Peter , Löhe Klaus 
Published: November 2019

AbstractConcerning the industrial process under investigation thin sheets are generated by squeezing material through a thin and actuated gap. Caused by improper settings or various disturbing control actions the sheets may exhibit residual stresses, and thus flatness defects. The aim of this work is to provide a modal analysis framework for visualization of these flatness defects.
Analysis of acoustic wave propagation in composite laminates via a spectral element method
Authors: Perras Elias , Zhang Chuanzeng 
Published: November 2019

AbstractThe analysis of the acoustic or elastic wave propagation phenomena in the time‐domain is computationally expensive. An often‐cited rule of thumb is to use at least ten nodes per wavelength if using quadratic shape functions, and even more nodes are necessary in order to achieve highly accurate numerical results. For large‐scale problems, this results in a large system of linear algebraic equations, which must be solved for several thousands of time‐steps. This requires a vast amount of the computing time. In this paper, a spectral element method (SEM), which is a variant of the finite element method (FEM) by using high‐order shape functions with non‐equidistant node distributions, is presented in order to investigate the acoustic wave propagation problems taking the fluid‐structure interaction into account with a minimum of required degrees of freedoms (DOFs). Hence, the computing time for solving the system of linear algebraic equations is reduced while maintaining a high accuracy. The element matrices are computed using the Lobatto quadrature method, which results in a diagonal element mass matrix. For fluid‐structure interaction problems in acoustics, a non‐symmetric sparse mass matrix is obtained. By using an explicit time‐integration scheme only the mass matrix becomes the coefficient matrix of the linear system and, due to its high sparsity, the solution process is very efficient. In this work, the SEM is implemented and applied for the analysis of the transient behavior of the laminated composite structures excited by acoustic waves. Numerical examples are presented and discussed to show the efficiency of the SEM in the time‐domain for applications in acoustic wave propagation problems considering the fluid‐structure interaction.
Reference material preconditioning for FFT‐based solvers
Authors: Ladecký Martin , Pultarová Ivana , Zeman Jan , Vondřejc Jaroslav 
Published: November 2019

AbstractProblems of finding effective material properties discussed in the classical works on homogenisation [1, 2] originate from asymptotic analysis of elliptic partial differential equations with oscillating anisotropic data. In 1994, Moulinec and Suquet [3] introduced an iterative algorithm for efficient determination of effective properties. In spite of its popularity and a deep research interest in this method, there are still some opportunities for improving its numerical effectiveness. We focus on preconditioning of related linear systems, which is necessary for solving large problems by iterative solvers. We introduce a general scheme for construction of preconditioning matrices based on some appropriate approximation of original material data.
Block partitioning of sparse rectangular matrices
Authors: Dumitrasc Andrei , Leleux Philippe , Rüde Ulrich 
Published: November 2019

AbstractWe present a means of reordering large, sparse rectangular matrices such that their nonzeros are closer to the diagonal. This enables a block‐partitioning which is useful in parallel contexts. We use the Reverse Cuthill‐McKee (RCM) algorithm on the adjacency matrix of the associated bipartite graph. The resulting, reordered matrix has a block bidiagonal structure.
FETI‐DP Solvers and Deal.II for Problems in Dislocation Mechanics
Authors: Köhler Stephan , Rheinbach Oliver , Sandfeld Stefan , Steinberger Dominik 
Published: November 2019

AbstractFETI‐DP (Finite Element Tearing and Interconnecting Dual‐Primal) solvers and the deal.II adaptive finite element library are combined to solve dislocation eigenstrain problems in micromechanics. Computational results using adaptive finite elements with millions of unknowns and up to 3072 cores of the Taurus supercomputer at ZIH in Dresden are presented.
Permeability and flow through a packed bed of beads in a rectangular cross‐section affected by overlapping wall effects
Authors: Boettcher Konrad , Neumann Tim , Ehrhard Peter 
Published: November 2019

AbstractThe beads in a packed bed are usually distributed randomly. Therefore, on a macroscopic scale, a fluid flows uniformly through such a porous medium. For thin porous media, deviations are known near the regions of confinement. This so‐called wall effect is extensively investigated in literature for circular confinements. In this work, the wall effect and the flow through porous media in a rectangular domain is studied. This has great importance during the initial filling process of lithium‐ion batteries with the liquid electrolyte. Such batteries consist of collector foils, on which the porous electrodes are attached. Their thickness is only 5 – 10 times a particle diameter dP and may be modeled as a monodisperse bed of spheres. The filling flow is extremely slow and may be in the pre‐Darcy flow region, wherefore the validity of Darcy‘s law is experimentally checked. Then, the local porosity function depending on the distance to the wall is experimentally determined. For very thin porous media, the wall effect of each wall may overlap each other, which is taken into account by using an overlapping model from the literature. The widely used model of Carman‐Kozeny [1] relates the permeability with the porosity. Its validity in the near‐wall region is checked by comparing experimentally‐obtained mean pore diameters to those related to the model of Carman‐Kozeny. The flow through a porous media is computed and compared to experimental results from literature for circular confinement and preliminary optically‐matched PIV measurements.
Molecular dynamics simulation of ultrasonic metal welding of aluminum alloys
Authors: Mostafavi Shimaalsadat , Markert Bernd 
Published: November 2019

AbstractIn this study, molecular dynamics simulation of the ultrasonic welding of aluminum alloys is presented. Ultrasonic metal welding is counted as a solid state consolidation of the mating parts, in which the growing interface temperature is far below the melting point of the material and the energy consumption is relatively low compared to the common welding processes such as arc welding. The reciprocating motion of the sonotrode on the mating parts combined with the application of external pressure in the process of ultrasonic welding is the source of temperature rise and strong plastic deformations at the mating interface. This contribution is devoted to study the interactive effect of the process parameters on the interface temperature, deformation process of the mating parts and the diffusion behavior of the interface atoms.
An Explicit Nash Equilibrium to a Multi‐Leader‐Follower Game
Authors: Steffensen Sonja , Thünen Anna 
Published: November 2019

AbstractThe multi‐leader‐follower game (MLFG) is a generalization of the Stackelberg game which considers bilevel games with a single leader. Here, the individuals (players) are divided into two groups, namely leaders and followers, according to their position (role) in the game. Mathematically, this yields a hierarchical Nash game, where further minimization problems appear in the leaders' optimization problems as constraints. A Nash equilibrium is then given by a multistrategy vector of all players, where no player has the incentive to change his chosen strategy unilaterally.We derive a Nash equilibrium for a quadratic multi‐leader‐follower game using the nonsmooth best response function of the follower. The existence and uniqueness of solutions are proven for an example and its Nash equilibrium is explicitly computed.
Gradient Enhanced Crystal Plasticity in Additive Manufacturing Identification of a Macroscopic Yield Criterion
Authors: Kergaßner Andreas , Mergheim Julia , Steinmann Paul 
Published: November 2019

AbstractIn this contribution the mechanical behavior of additively manufactured Inconel 718 (IN 718) is modeled on the meso and macro scale. Gradient enhanced crystal plasticity is utilized to capture the kinematics of crystallographic slips and grain boundaries on the meso scale. The material model is solved on a representative volume element (RVE) by means of the Finite Element Method. In order to represent additively manufactured material, the RVE is based on a numerical grain growth simulation of the solidification during additive manufacturing. Mesoscopic elastic behavior and the initial yield locus are transferred to the macro scale by numerical homogenization and used to identify the parameters for a quartic yield function which is able to capture the highly anisotropic material behavior.
Extended hypoplastic model incorporating the coordination number for the simulation of granular flow
Authors: Leon Bal Abdiel , Dang Thai Son , Meschke Günther 
Published: November 2019

AbstractIn this contribution, a hypoplastic viscous soil model incorporating viscous and grain‐inertia rate effects observed in granular flows is enhanced by means of the coordination number, which allows to characterize the evolution of the microstructure of the granular material. Near a critical solid volume fraction and critical coordination number there exists a transition from a solid‐like (rate‐independent) to a flow‐like (rate‐dependent) behavior of granular materials. This information is used to calibrate a so‐linear concentration factor, which controls viscous and grain‐inertial rate effects in terms of the rate dependent evolution of the coordination number. The influence of this proposed hypoplastic model considering the coordination number is investigated in this paper by means of a simple undrained shear test .
Simulating electromechanical delay across the scales – relating the behavior of single sarcomers on a sub‐cellular scale and the muscle‐tendon system on the organ scale
Authors: Schmid Laura , Klotz Thomas , Siebert Tobias , Röhrle Oliver 
Published: November 2019

AbstractThe time lag between the activation of a muscle and the development of force is commonly denoted as electromechanical delay (EMD). Within this work, a multi‐scale model of an idealized muscle‐tendon system is used to analyze EMD on different characteristic anatomical length scales. Thereby, the simluated EMD‐stretch curves for a complete muscle‐tendon system and a single sarcomere are significantly different. While for an isolated muscle EMD is shown to be strongly determined by excitation‐contraction coupling (ECC), the EMD‐stretch curve for a complete muscle‐tendon system is influenced by additional factors, such as, e.g., the tendon. Further, it is shown that the action potential conduction velocity (APCV) has minor influence on EMD.
Simulation of Dual‐Phase Steel Using the Finite Cell Method and Voxel‐Based Microstructure Data
Authors: Fangye Yannick F. , Miska Niklas , Balzani Daniel 
Published: November 2019

AbstractFor the modeling of micro‐heterogeneous materials, the effective macroscopic response can be determined by means of computational homogenization. The complex morphology of the microstructure needs to be discretized efficiently for numerical simulations. To reduce the effort arising from the generation of a conforming finite element mesh the finite cell method is applied. In this contribution, we focus on the microstructure of dual‐phase steel given by voxel‐based data and present an approach that directly exploits such data for an efficient generation of an integration mesh.