bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rotation‐Symmetric Referencebodys For Energy Efficient Flow Around Bodies
Authors: Quarti Michael , Gottlieb Andreas , Bühler Karl , Kachel Gerhard 
Published: December 2012

AbstractTopology optimization is used to optimize problems of flow around bodies and problems of guided flow. Within the context of research, optimization criteria are developed to increase the energy efficiency of these problems [1] [2] [3] [4] [5]. In order to evaluate the new criteria in respect to the increasing of energy efficiency, reference bodies for different Reynolds numbers in combination with given design space limitations are needed. Therefore, an optimal body at Reynolds number against 0 was analytically determined by Bourot [6]. At higher Reynolds numbers, in the range of laminar and turbulent flows, no analytical solution is known. Accordingly, reference bodies are calculated by CFD calculations at three technical relevant Reynolds numbers (1.000, 32.000, 100.000) in combination with parameter optimization. The cross section of the bodies is described by a parameterized model.To get the optimal body, a parameter optimization based on a “brute force”; algorithm is used to optimize with regard to the friction loss and pressure loss in order to minimize the total loss (cd‐value). The result is an optimal parameter constellation, depending on the Reynolds number. Within the results, it is possible to develop the optimal geometries. The identified characteristics of the flow field around these bodies are used as base for new optimization criteria. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stabilization of Laminar Boundary‐Layer Flow using Dielectric Barrier Discharge Plasma Actuators
Authors: Duchmann Alexander , Vieira Débora , Grundmann Sven , Tropea Cameron 
Published: December 2012

AbstractA numerical method is developed to study the stabilizing effect of dielectric barrier discharge plasma actuators on laminar boundary‐layer flow. A finite difference approach based on a Keller box discretization is chosen to solve the Falkner‐Skan transformed boundary‐layer equations. The fluid dynamic effect of the flow‐control device is implemented as a body‐force field, derived quantitatively from previous measurements using particle image velocimetry. The resulting laminar boundary‐layer flow is compared to experimental wind tunnel measurements and the effect on hydrodynamic stability is investigated in the framework of linear stability theory. A good agreement between experimentally acquired and numerically predicted transition locations based on an empirical function is obtained, rendering the numerical scheme valuable as a design tool for DBD based flow control applications. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the flow resistance of wide surface structures
Authors: Daschiel Gertraud , Baier Tobias , Saal Jürgen , Frohnapfel Bettina 
Published: December 2012

AbstractThe possibility of skin‐friction drag reduction in channel flows due to surface structures is investigated numerically. In this context, surface structures with a high width to height ratio compared to the typical dimensions of riblets are studied in the laminar as well as in the turbulent flow regime. In general, it is found that a reduction of the flow resistance is possible in both flow regimes. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Turbulent Flow with Embedded Vortical Structures Induced by Vortex Generators in a Cascade
Authors: Soucková Natálie , Uruba Václav 
Published: December 2012

AbstractPresented work is the next step after several experimental examinations of vortex generator influence on a flow separation occurring on a model of the NACA 63A421 airfoil with deflected simple flap. In this stage of research the vortices produced by vortex generators (VGs) were studied using Particle Image Velocimetry technique (PIV) and numerical simulations. Vane type VGs with two spacings among VGs pairs in straight channel with turbulent flow were tested. The average velocity flow field, peak of vorticity and circulation decay downstream of VGs were evaluated. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On an asymptotic upper‐convected Maxwell model for a viscoelastic jet
Authors: Lorenz Maike , Marheineke Nicole , Wegener Raimund 
Published: December 2012

AbstractIn this work we present a strict systematic derivation of a one‐dimensional upper convected Maxwell model (UCM) for the dynamics of a curved viscoelastic jet using asymptotic analysis in the slenderness ratio of the jet. The model does not pose any restrictions on shape and motion of the center‐line or the velocity profile. Numerical results are shown for stationary gravitational fiber spinning. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On Non‐linear Characteristics Evaluation of Vibratory Tool and Terrain Interaction for Embankment Works
Authors: Debeleac Carmen , Nastac Silviu 
Published: December 2012

AbstractThe complete and correct identification and evaluation of proper characteristics of terrain for embankment works is the frame idea of this analysis. The study began from the necessity of vibratory working tools utilization for different construction jobs. Mainly, the simple dynamic calculus is used for estimation of proper parameters values for this kind of works. It supposes a linear characteristic of the material in interaction with vibrating tool and it estimates the domain of working parameters. But instrumental tests reveal that the terrain has a non‐linear characteristic and the dynamic behaviour acquires deviation from theoretical estimations. An identification procedure followed by a correct and complete evaluation of the non‐linear parameters gives the necessary information for a practical case. Available mathematical models require a lot of initial values for characteristic parameters, but changing the case changes the values. A complex model which needs only initial tuning offers a proper solution to simulate, estimate, evaluate and analyze the interactions between the vibratory tools of construction equipments and the terrain. Non‐linear static and dynamic characteristics are the basic model defined properties. Elastic, dissipative and plastic rheological components were included into the main model. Partial concluding remarks have shown a good approximation between numerical results and experiments. The results of this study are very useful for vibratory equipment designing and correct exploitation, check of Regulations conformity for construction technologies, and oldies equipments maintenance. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Brownian dynamics of rigid body by fluctuating hydrodynamic equations
Authors: Pandey Anamika , Klar Axel , Tiwari Sudarshan 
Published: December 2012

AbstractIn this work, Brownian dynamics of rigid body in an incompressible fluid with fluctuating hydrodynamic equations is presented. To demonstrate the Brownian motion of rigid body, fluctuating hydrodynamic equations have been coupled with equations of motion of rigid body. Thermal fluctuation is included in the fluid equations via random stress terms unlike the random terms in the conventional Brownian dynamics type approach. Calculation of random stress terms in the fluid is easier in comparison to the random terms in the particle motion. Direct numerical simulation for the Brownian motion of rigid body with a meshfree framework is analysed. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Using the Elements of Manufacturing Systems Management in the Calculation of the Implementation of a Serial‐Modular Industrial Robot within a Flexible Work Cell Designed for Special Applications
Authors: Rizescu Alexandru Marius , Petrişor Silviu Mihai 
Published: December 2012

AbstractIn this paper, the authors propose a basic design of a flexible work cell with a parallel organization, destined for the spot welding of AAV carcasses. The cell is serviced by three industrial TTR robots that perform spot welding operations on the carcasses flowing on the conveyor belt to each of the robots performing this operation. This paper presents economic issues on the value of the robots comprised by the system, the calculus of the entire FWC value, the determination of the FWC static configuration, and evaluates the overall profitability of the cell using elements pertaining to the mathematical game theory and the graph theory, as well. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical optimisation of process parameters for combined quasi‐static and impulse forming
Authors: Rozgić Marco , Taebi Farhad , Stiemer Marcus 
Published: December 2012

AbstractMathematical optimisation of technological forming processes requires expensive simulations to evaluate objective function and constraint values as well as their derivative and Hessian informations. Therefore numerical linearisation methods like the finite difference method or the BFGS‐update are necessary. In this work the effects of these approximation techniques are studied. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Parameter identification based on multiple inhomogeneous experiments of practical relevance
Authors: Schellenberg Dirk , Juhre Daniel , Ihlemann Jörn 
Published: December 2012

AbstractExisting procedures to identify material parameters are based on experiments with simple specimens. Additionally, the load distribution is approximately homogeneous. But there are only few feasible experiments which produce homogeneous or almost homogeneous load distributions. Furthermore, deviations from homogeneity and their consequences cannot be avoided, but are often ignored. We present a solution algorithm which takes several different experimental results into account. Thereby, the experiments are performed on specimens which respond with inhomogeneous distributions of strains and stresses. The restriction to homogeneous loads is not necessary. Thus, it is possible to use different measured data of multiple load cases on one and the same test specimen. The component‐oriented design of the specimen permits to consider the specific properties of product groups, the load types and the effect of the manufacturing process on the final material properties already during the identification process. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Interpolation‐based solution of a nonlinear eigenvalue problem in fluid‐structure interaction
Authors: Effenberger Cedric , Kressner Daniel , Steinbach Olaf , Unger Gerhard 
Published: December 2012

AbstractA nonlinear eigenvalue problem arising from a coupled finite element/boundary element approach for fluid‐structure interaction is considered. We propose an approach based on polynomial interpolation and linearization for its numerical solution. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Application of Buckingham Π‐theorem to asymmetric plate rolling processes
Authors: Münker Tobias , Anders Denis , Weinberg Kerstin 
Published: December 2012

AbstractRolling under asymmetrical conditions such as temperature gradients within the material, difference of the circumferential velocity of the rolls and different friction coefficients cause the rolled slab to bend towards the direction of one of the rolls. In general this effect is undesired, since it hinders the further material transport and is a potential danger for the machine components in the proceeding processes. Unfortunately the essential mechanisms and the sensitivity of the influencing parameters in asymmetric rolling are still not comprehended sufficiently. Here a novel approach is presented in order to gain an enhanced insight into the front‐end bending phenomenon. To this end Buckingham Π‐theorem is applied to recover dimensionless coefficients describing the state of the roll gap and enable a reduction of the number of calculations in the required parametric studies. These parametric studies have been performed applying a finite element model considering elasto‐plastic material behaviour and the boundary conditions applied to the slab in the roll gap. The dimensionless quantity taking into account the slab's curvature is thoroughly investigated in terms of the other dimensionless system parameters. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Application of the Finite Pointset Method (FPM) to the kinetic BGK model
Authors: Kobert Maria , Kuhnert Joerg , Klar Axel 
Published: December 2012

AbstractThe BGK model of rarefied gas dynamics [1] is solved numerically by using the Finite Pointset Method (FPM) [2], which is a particle method developed at the ITWM Kaiserslautern. For the implementation a semilagrangian scheme [3] is used. Numerical results are shown on the example of a Shock tube problem for different Knudsen numbers. The solutions are compared to the solutions of exact Euler in the case of small Knudsen numbers and to DSMC solutions for higher Knudsen numbers. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Reduced Basis Method for Time‐Harmonic Maxwell's Equations
Authors: Benner Peter , Heß Martin 
Published: December 2012

AbstractThe Reduced Basis Method (RBM) generates low‐order models of parametrized PDEs to allow for efficient evaluation of the input‐output behaviour in many‐query and real‐time contexts. The RBM approach is decomposed into a time‐consuming offline‐phase, which generates a surrogate model and an online phase, which performs fast parameter evaluations. Rigorous and sharp a posteriori error estimators play a crucial role in the greedy process to generate the surrogate model and give bounds to the output quantities in the online phase.We show the theoretical framework in which the Reduced Basis Method is applied to Maxwell's equations arising from semiconductor interconnect structures and present first numerical results for model reduction in frequency domain. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Algebraic graph theory and its applications for mesh generation
Authors: Schröppel Christian , Wackerfuß Jens 
Published: December 2012

AbstractMesh generation is an important step in many numerical methods. The authors present a novel approach to mesh generation, based on algebraic graph theory, that can be used to systematically construct configurations exhibiting multiple hierarchies and complex symmetry characteristics. The mesh is expressed as a hierarchically symmetric graph that preserves both the hierarchical structure as well as the symmetry characteristics of such configurations. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A finite volume element method for simulating secondary settling tanks
Authors: Bürger Raimund , Ruiz‐Baier Ricardo , Torres Héctor 
Published: December 2012

AbstractThis contribution summarizes a new finite volume element (FVE) method as a unified scheme for coupled sedimentation‐flow problems in secondary settling tanks in wastewater treatment. The model is two‐dimensional in an axisymmetric setting. A new numerical example is presented. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A finite element method for a noncoercive elliptic problem with Neumann boundary conditions
Authors: Kavaliou Klim , Tobiska Lutz 
Published: December 2012

AbstractWe consider a noncoercive convection‐diffusion problem with Neumann boundary conditions appearing in modeling of magnetic fluid seals. The associated operator has a non‐trivial one‐dimensional kernel spanned by a positive function. A discretization is proposed preserving these properties. Optimal error estimates in the H1‐norm are based on a discrete stability result. Numerical results confirm the theoretical predictions. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Phase lag analysis of variational integrators using interpolation techniques
Authors: Kosmas O.T. , Leyendecker Sigrid 
Published: December 2012

AbstractIn the present work we derive higher order variational integrators and combine them with phase lag properties for the numerical integration of systems with oscillatory solutions. The discrete Lagrangian in any time interval is defined as a weighted sum of the evaluation of the continuous Lagrangian at intermediate time nodes. The expressions used for configurations and velocities use linear interpolation, cubic spline interpolation or interpolation via trigonometric functions. The new methods depend on a frequency, which needs to be chosen appropriately. Results show that the energy error of the integration method is decreased for good frequency estimates. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Derivation of an adjoint high‐Reynolds number model for thermally driven flows
Authors: Lincke Anne , Stück Arthur , Rung Thomas 
Published: December 2012

AbstractThis paper presents a high‐Reynolds number (high‐Re) approach to the adjoint Navier‐Stokes‐Fourier equations based upon modified high‐Re boundary conditions for buoyancy‐driven flows. For reasons of efficiency, the computational framework adheres to the continuous adjoint method using a frozen‐turbulence assumption. Opposed to the state of the art, the present model uses a high‐Re model for the primal equations and a high‐Re model for the adjoint equations. The adjoint high‐Re model can easily be implemented and be used for flow problems where wall functions are needed. The impact of this approach is an improved consistency of primal and adjoint equations which leads to stable and realistic shape optimisation results for industrial flows. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An Approach to Shape Optimization with State Constraints
Authors: Leithäuser Christian , Feßler Robert , Pinnau René 
Published: December 2012

AbstractWe introduce a new approach to solve shape optimization problems with state constraints. The problem is reformulated on a fixed reference domain using conformal pull‐back. The shape dependence is then hidden in the conformal parameter. The problem is discretized using FEM and solved as an NLP. Finally the optimal shape can be reconstructed from the optimal conformal parameter. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multilevel optimization for PDAE‐constrained optimal control problems with pointwise constraints on control and state
Authors: Clever Debora , Lang Jens 
Published: December 2012

AbstractWe have developed a fully adaptive optimization environment suitable to solve complex optimal control problems restricted by partial differential algebraic equations (PDAEs) and pointwise constraints on the control [1, 2]. This contribution is devoted to the inclusion of pointwise constraints on the state within the optimization environment. To this end we first give a brief introduction into the architecture of the environment and the inclusion of pointwise constraints on the state by Moreau‐Yosida regularization. Then, we test the new tool by applying it to an optimal boundary control problem for the cooling of hot glass down to room temperature, modeled by radiative heat transfer and semi‐transparent boundary conditions. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
POD and CVT Galerkin reduced‐order modeling of the flow around a cylinder
Authors: Ullmann Sebastian , Lang Jens 
Published: December 2012

AbstractReduced‐order models are applied to the laminar vortex‐shedding flow around a circular cylinder. The models rely on approximations of the solutions in the space spanned by a set of POD or CVT reduced basis vectors, which are computed from snapshots of a numerical solution. To enable the computation of drag and lift forces, the modeling of the velocity and pressure is realized via a one‐way coupling. A comparison of the results of the CVT and POD reduced‐order models is presented. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Zero crossings in the step response of linear time‐delay systems
Authors: Damm Tobias , Muhirwa Luc N. 
Published: December 2012

AbstractRelations between zeros of the transfer function and properties of the step response are quite well‐known for linear time‐invariant systems. In this paper we provide new derivations of some of these results about zero crossings which immediately allow a generalization to systems with time‐delay. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An Approach for Parameter Identification in Distributed Parameter Systems
Authors: Knüppel Torsten , Woittennek Frank 
Published: December 2012

AbstractIdentification of physical parameters in systems modelled by linear partial differential equations (p.d.e.) from lumped measurements is considered. The problem is solved by means of an alternative formulation of the boundary value problem as convolutional system. The approach allows for the identification even in the presence of non‐homogeneous initial conditions. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Orbital stabilization of a class of underactuated mechanical systems
Authors: Knoll Carsten , Röbenack Klaus 
Published: December 2012

AbstractTypically, the aim of a controller is to stabilize an equilibrium or a reference trajectory. For underactuated mechanical systems this objective might not be achievable because of the occurance of limit cycles due to discontinuous effects like actuator backlash or Coulomb friction. Therefore, an alternative approach is to explicitly impose a stable periodic orbit on the system by a suited controller. This way at least amplitude, frequency and settling time can be influenced directly. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Computationally efficient receding horizon trajectory tracking control for a tubular reactor example
Authors: Utz Tilman , Graichen Knut 
Published: December 2012

AbstractFlatness‐based feedforward control and receding horizon trajectory tracking control can be combined within a two‐degrees‐of‐freedom (2dof) control scheme to obtain robust trajectory tracking for nonlinear systems. The key to a computationally efficient solution of the optimization problem underlying the receding horizon control is the linearization of the time‐variant tracking error dynamics such that the nonlinear optimal control problem may be replaced by a linear‐quadratic formulation. The approach is demonstrated for setpoint transitions of a nonlinear boundary‐controlled parabolic partial differential equation (PDE), which is semi‐discretized for the control design using finite differences on the spatial derivatives. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Identification of transmission line parameters using algebraic methods
Authors: Gehring Nicole , Rudolph Joachim , Stauch Christian 
Published: December 2012

AbstractAn algebraic approach to parameter identification for transmission lines using boundary measurements is suggested. The class of systems under consideration can be modelled by means of linear partial differential equations (p.d.e.s). It includes examples from different technological domains such as the telegrapher's equations or models for fluid transmission lines. The main idea of the approach presented is to generate a set of equations involving only boundary measurements and parameters in such a way that they can easily be interpreted in the time domain. To this end, the system's p.d.e.s are written in terms of o.d.e.s (ordinary differential equations) using Mikusiński's operational calculus. The proposed identification method is illustrated considering a fluid transmission line model with laminar flow and frequency dependent viscous friction. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Some remarks concerning differential flatness and tangent systems
Authors: Franke Matthias , Röbenack Klaus 
Published: December 2012

AbstractThe flatness properties of a nonlinear dynamical control system are completely characterized by its tangent approximation. The flat output of the nonlinear system can be obtained (at least from a theoretical point of view) by solving an integrability problem for the flat outputs of the tangent system. In the present contribution, this approach is used to easily obtain flatness conditions for two special classes of systems, namely systems with one input and systems with one input less than states. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)