bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inverses Rechnen zur Identifikation der Materialparameter des Cosserat‐Kontinuums
Authors: Scholz Bernd , Ehlers Wolfgang 
Published: April 2003

AbstractBei der Anwendung der Cosserat‐Theorie treten neben den Verschiebungsfreiheitsgraden zusätzliche Rotationsfreiheitsgrade auf. Zur Beschreibung der Deformation wurden demzufolge ein nicht‐symmetrischer Verzerrungstensor sowie ein Krümmungstensor eingeführt. Diesen erweiterten Deformationsmaßen werden über konstitutive Beziehungen ein nicht‐symmetrischer Spannungstensor sowie ein Momentenspannungstensor zugeordnet. Dabei treten neue Materialparameter (z. B. die interne Länge) auf, deren Identifikation das Ziel der vorgestellten Arbeit ist. Da die zusätzlichen Rotationsfreiheitsgrade nur bei inhomogener Deformation aktiviert werden, sind zur Bestimmung der Materialparameter des Cosserat‐Kontinuums inhomogene Versuche sowie deren Nachrechnung als Randwertproblem erforderlich. Dazu stehen an Hostun‐Sand durchgeführte Biaxialversuche zur Verfügung.
Contribution to the propeller aerodynamic interference
Authors: Vrdoljak Milan 
Published: April 2003

AbstractPropeller wake can significantly change the flowfield at the downstream lifting surfaces and therefore influence its aerodynamic coefficients. The numerical model of the propeller presented here is using discrete vortices to form vortex sheet that is leaving each blade. Model is also applicable for combination of lifting surface and propeller using undeveloped propeller vortex sheet in determination of aerodynamic interference of the propeller on the downstream lifting surface, wing or tail for small angle of attack. This low computational cost numerical model is suitable for implementation in component build–up method used in preliminary estimation of aerodynamic coefficients for different propeller aircraft configurations.
Parallele numerische Strömungssimulation bei Fluiden mit Gedächtnis
Authors: Andoleit B. 
Published: April 2003

AbstractEs wird ein Verfahren zur numerischen Simulation einer stationären, isothermen und schleichenden Strömung eines inkompressiblen, viskoelastischen Fluides beschrieben. Die Gedächtnisintegrationen wird, nicht wie herkömmlich auf einem Prozessor, sondern parallel auf mehreren Prozessoren durchgeführt.
An Applicable Boundary Condition at the Moving Contact Line in Case of a Free Surface Reorientation after Step Reduction in Gravity
Authors: Gerstmann J. , Michaelis M. , Dreyer M. , Rath H.J. 
Published: April 2003

AbstractIn this study the sudden change in the acceleration level on a free surface in a right circular cylinder is investigated numerically. The intention to describe the .uid motion encounters the difficulty modelling the moving contact‐line problem. In the numerical simulations the Navier slip boundary condition and a model for the dynamic contact angle are used. The model for the dynamic contact angle γd includes the dependence on the Capillary number as well as the contact angle hysteresis. We achieved very good agreement with experimental data.
New Zonal, Spectral Solutions for the Navier‐Stokes Layer and Their Applications
Authors: Nastase A. 
Published: April 2003

AbstractNew zonal, spectral forms for the axial, lateral and vertical velocity's components, density function and absolute temperature inside of compressible three‐dimensional Navier‐Stokes layer (NSL) over flattened, flying configurations (FC), are here proposed. The inviscid flow over the FC, obtained after the solidification of the NSL, is here used as outer flow. If the spectral forms of the velocity's components are introduced in the partial differential equations of the NSL and the collocation method is used, the spectral coefficients are obtained by the iterative solving of an equivalent quadratical algebraic system with slightly variable coefficients.
Film flow over strongly undulated bottom profiles at low Reynolds numbers – Analytical results
Authors: Scholle Markus , Wierschem Andreas , Aksel Nuri 
Published: April 2003

AbstractFilm flows occur in many technical processes (e.g. coating techniques) as well as in nature. In this paper we establish a new analytical method in order to calculate both the velocity field and the surface shape of a two–dimensional gravity driven film flow of a Newtonian fluid down a periodically varying bottom topology. We discuss the special case of a sinusoidal bottom shape.
Analytische Lösungen zur Oszillirenden Rohrströmung für einige nichtkreisförmige Rohrquerschnitte
Authors: Zlatanovski T. 
Published: April 2003

AbstractDas Ziel dieser Arbeit ist, mögliche analytische Lösungen zur oszillierenden Strömung einer newtonschen oder viskoelastischen Flüssigkeit durch gerade Rohre von nichtkreisförmigem Querschnitt zu erhalten. Im Falle oszillierender Strömung einer viskoelastischen Flüssigkeit beschäftigt uns im besonderen die analytische oder numerische Berechnung der in der Querschnittsebene existierenden Sekundärströmung, die bei der laminaren Rohrströmung einer newtonschen Flüssigkeit oder im Falle des kreisförmigen Rohrquerschnittes nicht in Erscheinung tritt.
LES of a Confined Configuration using Oscillating Inflow Conditions
Authors: Düsing Michael , Sadiki Amsini , Janicka Johannes 
Published: April 2003

AbstractIn actual turbulent flow problems, in particular in gas turbine combustion chambers, flows are three dimensional, recirculating and turbulent in confined and complex geometries. Instationarities due to turbulence, combustion instabilities and oscillating inflow conditions require a highly time and spatial resolving procedure. 3D Large Eddy Simulations (LES) are therefore used in this work to study two confined coaxial air jets with oscillating velocity inflow conditions. The influences of the inflow, in particular frequency (f = 0 ÷ 1600 [Hz]) and amplitude, on the velocity are analysed.
Direct Numerical Simulation of Hypersonic Flow over a Cavity
Authors: Klutchnikov I. , Ballmann J. 
Published: April 2003

AbstractAn open rectangular cavity has served as a generic geometry in shock tunnel experiments with laminar flow being two‐dimensional upstream of the cavity. A high order central difference scheme with flux‐corrected transport has been employed to simulate the flow under the assumption that the inflow profile upstream of the cavity is laminar. The high order in space enables to reproduce well vortical structures and possible transition to turbulent flow.
Application of harmonic polynomials as complete solutions of Laplace equation in an inverse heat conduction problem
Authors: Hożejowski L. , Hożejowska S. , Piasecka M. 
Published: April 2003

AbstractThe area of interest is the issue of heat transfer into Freon 123 flowing through a narrow vertical channel. The paper presents a computational procedure whose aim is to determine a local heat transfer coefficient. In the described experiment thermosensitive liquid crystals were used for measuring temperature on the heating surface. Since the temperature distribution can be approximated with a linear combination of harmonic polynomials, the heat transfer coefficient is expressed with the use of these polynomials. solving differential equations, PWN, Warszawa 1960 (in Polish)
Numerical Investigation of Particulate Flow over a Backward‐Facing Step
Authors: Kubik A. , Kleiser L. 
Published: April 2003

AbstractFlow separation and recirculation caused by a sudden expansion in the channel geometry in the form of a backwardfacing step (BFS) appear in numerous practical applications. Additionally, BFS flow has been used as a generic test case to study fundamental flow properties, such as separation or re‐attachment. In the present work, BFS flow laden with dispersed particles is investigated by numerical simulations using a spectral element method [1]. The motion of the dispersed particles is computed by Lagrangian particle tracking. In a first step, only the influence of the flow on the particles is accounted for, while possible effects of the particle motion on the flow are neglected. Spatial distribution of the particles is investigated, and effects of different wall‐particle interaction models on the computational results are examined.
Transport of fluids in capillary porous solids
Authors: Ricken Tim 
Published: April 2003

AbstractCapillarity is a well known phenomenon in physics and engineering. The term denotes the transport of liquids and gas, against the force of gravity in narrow tubes, cracks and pores, caused by the intermolecular forces of cohesion and adhesion of the constituents involved. We will exclusively investigate the rise of liquids in porous bodies due to the capillarity phenomenon. Well‐known examples are the capillary rise in drying processes in soils with small pores and the moisture motion in walls consisting of bricks or concrete. The treatment of the capillary problem, based on thermomechanical investigations, yields the result that the capillarity force is a volume interaction force and depends on the free Helmholz energy functions of the solid phases and the density gradient of the liquid. The aim of this investigation is the numerical simulation of the behavior of liquid and gas phases in a rigid porous body at rest. An example will demonstrate the usefulness of the proposed theory.
Modified k – ω Model for Simulation of Cavitating Flows
Authors: Sorgüven Esra , Schnerr Günter H. 
Published: April 2003

AbstractAlthough cavitating flows are generally turbulent, the interaction of turbulence and cavitation dynamics is still not well understood. In general, two‐equation models are employed, which were originally developed for single‐phase flows. Therefore they fail by handling cavitation based flow phenomena with very high density variations (dependent on operating condition up to 40000:1). This sudden change of the density causes strong pressure gradients, secondary flows and local compressibility. The aim of this study is to enhance the Wilcox's k‐? model with empirical correlations in order to simulate turbulent cavitating flows more precisely and effciently.
The Structure of Dispersion Relation in Hyperbolic Thermoelasticity
Authors: Dobovšek Igor 
Published: April 2003

AbstractFor a system of field equations of hyperbolic thermoelasticity we derive a propagation condition for a thermoelastic disturbance in a form of homogeneous plane wave in deformation and temperature. The corresponding dispersion relation is given in an explicit form, together with the discussion of di.erent types of homogeneous thermoelastic plane waves that may emerge from the resulting system of coupled PDEs.
Zur Berechnung der Schallabstrahlung umströmter Körper
Authors: Rung T. , Eschricht D. , Yan J. , Thiele F. 
Published: April 2003

AbstractDieser Artikel behandelt die Berechnung des abgestrahlten Lärms umströmter, stumpfer Körper. Das Verfahren beruht dabei auf der Trennung von Quellberechnung und Ausbreitung des Schalls ins Fernfeld. Die Fernfeldberechnung erfolgt auf Grundlage der Gleichung von Ffowcs‐Williams und Hawkings. Der hierzu verwendete Löser wird anhand analytischer Lösungen der linearen Wellengleichung validiert. Das Verfahren wird auf die Umströmung eines generischen Fahrzeugaußenspiegels mit Re=5.2×105 angewendet, für den experimentelle Daten als Vergleich vorliegen. Die Simulation der Quellen erfolgte dabei mit einer Detached‐Eddy Simulation.
Structure of weak laminar hydraulic jumps in single layer and two layer fluids
Authors: Kluwick A. , Exner A. , Cox E.A. 
Published: April 2003

AbstractWe consider the occurrence of hydraulic jumps in near critical single layer and two layer flows under the assumption that viscous effects are confined to a thin laminar boundary layer adjacent to the solid boundary. In the limit of large Reynolds number this leads to a structure problem formed by the classical triple deck equations supplemented with a novel nonlinear coupling condition which allows for the passage through the critical state. In the case of positive hydraulic jumps this passage is achieved by the local thickening of the boundary layer which acts as a viscous hump. Conversely, the pressure drop at the wall associated with negative hydraulic jumps causes the boundary layer to decrease locally thereby forming a local indentation required for the Froude number to pass through one in this case.
Existence and Approximation of Solutions of a System of Quasilinear Differential Equations
Authors: Omerspahić Alma 
Published: April 2003

AbstractThis paper deals with the behavior, approximation and stability of some solutions of the system of quasilinear differential equations. The behavior of solutions in the neighbourhood of an arbitrary curve is considered, with extraordinary attention on some special cases. The obtained results contain an answer to the question on approximation as well as stability of solutions whose existence is established. The errors of the approximation are defined by the function that can be sufficiently small. The theory of qualitative analysis of differential equations and topological retraction method are used.
A fast method to implement non‐local discrete transparent boundary conditions for the Schrödinger equation
Authors: Arnold A. , Ehrhardt M. , Sofronov I. 
Published: April 2003

AbstractDiscrete transparent boundary conditions (DTBCs) for the time‐dependent Schrödinger equation were introduced in the numerical simulations of whole space problems in order to reduce the computational domain to a finite region. They include a convolution w.r.t. time with a weakly decaying kernel that leads to very costly numerical evaluation for large‐time simulations. As a remedy we construct approximate DTBCs with a kernel having the form of a finite sum‐of‐exponentials, which can be evaluated in an efficient recursion.
Dimension Reduction methods for Infinite Dimensional Systems
Authors: Steindl Alois 
Published: April 2003

AbstractFrom experiments and also from computer simulation of dynamical systems it is well known that for many dynamical phenomena in physics or engineering, which are modelled by infinite dimensional dynamical systems, the asymptotic behavior can be accurately described by replacing the original infinite dimensional system by a low dimensional system represented by so‐called essential variables. Such a dimension reduction of a dynamical system turns out to be central, both for a qualitative and quantitative understanding of its behaviour.In [1] Approximate Inertial Manifolds are presented, which perform extremely well for nonlinear evolution equations, but don't work as expected for the dynamics of a fluid conveying tube. By comparing the results for different internal damping values it can be seen that the larger gaps and the location of the cluster point in the spectrum for the weaker damping improve the approximation quality considerably.
Knowledge‐based Diagnosis Aiding in Regulation Thermography
Authors: Knaf Hagen , Lang Patrick 
Published: April 2003

AbstractRegulation Thermography is a diagnostic tool in the medical science based on the measurement of the body's thermoregulation ability – the so‐called thermogram. The expert's rules for the interpretation of a thermogram can be modelled using Fuzzy Logic. In the present article this modelling process is briefly explained; it leads to a Fuzzy Inference System capable of evaluating thermograms with respect to e.g. signals for the presence of Breast Cancer. Some of the main points of a comparison between the expert rules and the result of a stepwise linear discriminant analysis performed on classified thermograms are presented.
Phase Coexistence and Critical Point of the Stell‐Hemmer Fluid
Authors: May H.‐O. , Mausbach P. 
Published: April 2003

AbstractBy means of a Gibbs ensemble Monte Carlo method we calculate the gas‐liquid coexistence line for a Stell‐Hemmer fluid in three dimensions. We estimate the critical point using a scaling law where the critical exponent is β = 0.32.
Interval Arithmetic in Maple with intpakX
Authors: Grimmer Markus 
Published: April 2003

AbstractintpakX, a Maple package for interval arithmetic created in 1999 by I. Geulig and W. Krämer [1,3], is based on intpak, an experimental Maple package that was created by A.E. Connell and R.M. Corless in 1993 [2].intpakX contains basic data types and operators for interval arithmetic as well as a variety of numerical methods using intervals. It offers the possibility to compute verified numerical results with a Computer Algebra System and at the same time display the results graphically.With the new version intpakX v1.0, intpakX has been updated and redesigned to work with Maple7. This paper shows the range of features of intpakX and gives some examples of their use.
Transient RankingMethods for the Simplification of Nonlinear DAE Systems in Analog Circuit Design
Authors: Wichmann Tim 
Published: April 2003

AbstractSymbolic analysis of analog circuits using computer algebra is limited by the complexity problem: even for small circuits the symbolic equation systems get too large to be handled efficiently. In the past years simplification techniques have been developed which reduce the complexity of such equation systems. In this paper we are focusing on simpli fication techniques for equations modeling nonlinear transient analog circuits. Here it is necessary to control the dynamic behavior of the simplified system. For this, we developed two different methods which predict the influence of a simplification on the equations' transient solution. We will describe both methods and compare their efficiency and accuracy.
On Fuzzy Logic Compenstion System of Irregular Disturbances in a Process of Fine Machining
Authors: Kacalak W. , Lipiński D. , Krzyżyński T. , Lenartowicz M. 
Published: April 2003

AbstractIn the paper the analysis of sources and results of irregular disturbances in a process of fine machining is presented. A description of events causing the disturbances and an advisability of use of thermal and elastic systems for compensating relative position deviations of cutting tool and a piece are given. A compensation system with the application of fuzzy logic and detailed algorithms and programs for various compensation strategies are proposed. It is shown that compensating actions should depend on a present relative tool‐piece position and its first derivative.
On Optimisation of Detail Recognition in a Process of Super‐Fast Grinding of Ceramics
Authors: Lenartowicz M. , Krzyżyński T. , Lipiński D. , Kacalak W. 
Published: April 2003

AbstractMost of digital picture processing systems are used in mass production. While making use of intelligent systems of standard recognition, digital picture processing can be applied in lot production or small lot production, and their ability to learn enables them to recognize parts of di.erent shapes. In the present paper, a system based on fuzzy logic principles was introduced. It has an application in the automation of the feed of machined elements into the machine working space during machining of ceramics.
Gestaltoptimierung von Bögen für verschiedene Belastungsfälle
Authors: Mikulski Leszek 
Published: April 2003

AbstractIn dieser Arbeit widmen wir uns der Gestaltoptimierung von Bögen, die simultan verschiedenen Belastungsfälle aushalten und dabei die maximale Verschiebung (Spannung) minimal halten. Die optimierten Bögen besitzen längs ihrer Länge einen veränderlichen Querschnitt, sind durch Eigengewicht und Nutzlast belastet. Betrachtet werden verschiedene Fälle gleichzeitiger Belastung der Bögen, z.B. für einen Bogen mit zwei inneren Unterstützungen werden sechs verschiedene Belastungsfälle angenommen. Als Optimierungskriterium wird die maximale Verschiebung oder die maximale Spannung ausgewählt. Die Querschnittshöhe und die Lage der inneren Unterstützungspunkte sind die veränderbaren Steuergrößen in dieser Aufgabe. Die Nebenbedingungen (Beschränkungen) sind geometrischer Art, die Steuergrößen und das Gesamtgewicht des Bogens betreffend. Die Probleme der Gestaltoptimierung lassen sich mathematisch als optimale Steuerungsprobleme formulieren. Zur Lösung der hier formulierten Problemstellung wird das Maximumprinzip verwendet. Das Maximumprinzip erlaubt es, das Problem der optimalen Gestaltung als ein Mehrpunktrandwertproblem (MPRWP)für ein Differentialgleichungssystem aufzuschreiben. Die Dimension des MPRWP stellt üblicherweise eine große Beschränkung dar und entscheidet über numerische Schwierigkeiten. Für die numerische Lösung wird das Hybridverfahren verwendet, welches eine Verbindung der Mehrziel und Kollokationsmethode ist. Die Aufgabe wurde mit einem leistungsfähigen Programm Dircol gelöst.
Constraint preconditioning for linear systems in elasticity
Authors: Geilenkothen A. 
Published: April 2003

AbstractThe mixed variational formulation of elastic deformation of a material body leads to a constraint minimisation (or saddle‐point) problem. Using the PEERS finite element space to discretise the problem one gets an indefinite system of linear equations. To solve this system, preconditioners with similar saddle‐point patterns will be applied. The results of numerical tests with this preconditioning strategy show its efficiency for linear systems with up to more than half a million unknowns.
The streamline–diffusion method for a convection–diffusion problem with a point source
Authors: Roos Hans–Görg , Zarin Helena 
Published: April 2003

AbstractA linear singularly perturbed convection–diffusion problem with a point source is considered. The problem is solved using the streamline–diffusion finite element method on a class of Shishkin–type meshes. We prove that the method is almost optimal with uniform second order of convergence in the maximum norm. We also prove the existence of superconvergent points for the first derivative. Numerical experiments support these theoretical results.
Dynamic iteration may fail for partitioned network simulation
Authors: Günther Michael 
Published: April 2003

AbstractIn many technical applications, complex systems are composed of subsystems that are modelled independently using a network approach. This co‐modelling ansatz is completed very naturally by a co‐simulation approach based on dynamic iteration, where the respective DAE submodels are solved iteratively. For partitioned electric network simulation we show that this approach may fail. As alternative we discuss overlapping techniques based on topological network information.
On A‐stability for some two‐step W‐methods
Authors: Podhaisky H. , Weiner R. , Schmitt B.A. 
Published: April 2003

AbstractIn this paper we prove the A‐stability for some sequential and parallel two‐step W‐methods (TSW‐methods and PTSW‐methods) which have been constructed recently for the numerical solution of large stiff ODE systems. To show that the spectral radius of the amplification matrix of a fixed method is less than one we apply Schur's criterion recursively to the characteristic polynomial of the amplification matrix. The computations can be done automatically using computer algebra tools, e.g. Maple 7.