bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical solution of flow through a cascade and over a profile with dynamicaland aeroelastic effects
Authors: Honzátko R. , Horáček J. , Kozel K. 
Published: June 2004

AbstractThe work deals with a numerical solution of 2D inviscid incompressible flow through a cascade and over a profile in a channel. The finite volume method in a form of cell‐centered scheme at triangular and qudrilateral mesh is used. The composite scheme applied to a numerical solution consists of more dissipative part (Lax‐Friedrichs scheme) and less dissipative part (Lax‐Wendroff scheme). Governing system of equations is the system of Euler equations. Two possibilities are considered.
Description for smooth contact conditions based on the internal geometry of contact surfaces
Authors: Konyukhov Alexander , Schweizerhof Karl 
Published: June 2004

AbstractA kinematical approach, based on the consideration of the contact conditions in the local coordinate system, is proposed for the contact description and for consistent linearization. This leads to a simple structure of the tangent matrix, which is subdivided into main, rotational and curvature parts. Various alternatives neglecting parts of the contact tangent matrix are considered. Representative examples show the effectiveness of the proposed approach for contact problems with arbitrary large deformation.
Modeling and finite element formulation of piezoelectric fiber compositebeams
Authors: Lammering Rolf , Brockmann Tobias H. 
Published: June 2004

AbstractPiezoelectric fiber composites with their dynamic characteristics, tailorable anisotropic properties, and high degree of integration provide excellent prospects for structural actuation tasks. An active beam concept with such a material system can be applied to helicopter rotor blades in order to reduce vibrations and noise. The most effective way to actively influence the blade dynamics is to make use of the aerodynamic forces by changing the angle of attack. Thus the goal is to investigate the potential of induced torsion and its different possible actuation schemes on the dynamic behavior of the rotating system. For this purpose a finite beam element formulation is derived and tested successfully.
Finite Element Simulation of Smart Structures for Active Vibration andAcoustic Control
Authors: Lefèvre Jean , Gabbert Ulrich 
Published: June 2004

AbstractThe design process of engineering smart structures using piezoelectric patches as distributed sensors and actuators requires a virtual overall model, which includes the main functional parts. In the paper a suitable software tool based on the FEM is presented to simulate coupled electro‐mechanical‐acoustical problems regarding interior noise problems. The modal truncation technique is used to design a LQ‐controller as well as to study the time‐depending behaviour of a clamed smart plate.
Aspects of Computational Modeling of Discontinuities with Enriched Triangular Finite Elements
Authors: Löblein J. , Schröder J. 
Published: June 2004

AbstractIn this paper the simulation of discrete cracks using triangular finite elements with an embedded interface is discussed. The formulation based on [2] is extended to geometric nonlinearity. The derivation starting from the kinematics for a divided body and the corresponding weak form of equilibrium is briefly described. Furthermore, some details concerning the numerical implementation are outlined. Finally, a three‐point bending test is analyzed.
Discrete methods for soil modelling
Authors: Nardin A. , Schrefler B. A. , Zavarise G. 
Published: June 2004

AbstractThe interaction of the cutting tools with different geological settings determines a different wear and consequently different economical costs for the excavation. We apply here a strategy for soil modelling which is based on discretization of the continuum with rigid disks and suitable contact models. We concentrate at contact level the real mechanical behaviour of the soil. In order to carry out this strategy a “micro” and a “macro” level are established. This paper focuses on the micromechanical model.
Beanspruchungen des Unterkiefers bei unterschiedlichen Implantatverteilungen und unter unterschiedlichen Lasten
Authors: Rues Stefan , Lenz Jürgen , Schindler Hans J. , Rong Qiguo , Schweizerhof Karl , Riediger Dieter 
Published: June 2004

AbstractMit Hilfe der Methode der Finiten Elemente werden für unterschiedliche, häufig verwendete (symmetrische und nicht‐symmetrische) Implantatverteilungen im Unterkiefer die Spannungen im periimplantären Knochenbett analysiert, insbesondere um klinisch‐kritische Beanspruchungen zu bewerten. Die Analyse zeigt, dass die Druckspannungen mit wachsendem Atrophiegrad des Kiefers ansteigen und dass eine zusätzliche Schleimhautabstützung zu einer beträchtlichen Reduktion der Spannungen im Implantatbett beitragen kann.
Bending design of reinforced concrete circular cross sections after EC2 standard for strain εc2 smaller than 1.35‰
Authors: Skrinar M. 
Published: June 2004

AbstractThe paper discusses the bending analysis of a concrete circular cross section using the bilinear stress distribution for the design stress‐strain relationship of the concrete according to the EC2 standard for the case when the absolute maximal strain in the concrete does not exceed the value of 1.35‰
Fixed‐point type iterations in numerical simulations for static and dynamic elastoplasticity
Authors: Vetyukov Yury , Gerstmayr Johannes , Irschik Hans 
Published: June 2004

AbstractDynamics of the elastoplastic media is stated in terms of plastic eigenstrains acting upon a background elastic problem with fixed (initial) stiffness. The plastic flow is described by specifically introduced plastic multipliers, which minimizes the number of unknown variables to be determined within the time step. A fixed‐point type iteration strategy is suggested for the computation of the plastic multipliers, which has been implemented for the finite element spatial discretization. Numerical experiments show the correctness and the effectiveness of the developed algorithm.
Consistent Transition of Beam‐Shell Structures within the FE Method
Authors: Wenzel Michael 
Published: June 2004

AbstractIn this paper we present a finite transition element for a consistent coupling of beam and shell structures. Often thin‐walled beam structures are calculated with beam elements. In order to achieve low modelling and calculation costs this is a useful procedure. For some reasons, e.g. local buckling or global collapse like torsional‐flexural buckling, it is necessary to model high loaded regions of a structure with shell elements within the beam model. For this kind of dimensional adaptivity the transition element is developed.
A Procedure for Identification of Friction Parameters in Constrained Robots
Authors: Fenili A. , Schäfer B. 
Published: June 2004

AbstractPrecise manipulation of objects in space by robotics requires the knowledge of contact parameters. These physical parameters change with outer space environmental impacts. On‐orbit experiments for in situ parameters identification are being prepared, and a simplified problem regarding the identification of friction coefficients is addressed in this paper. The development of a reliable contact model, that includes a complete knowledge about the robot parameters is adressed here. The parameters identification is based on a least square algorithm.
Wavelet‐based nonparametric identification technique for nonlinear dynamic systems
Authors: Glabisz Wojciech , Koźbiał Tomasz , Napiórkowska Magdalena 
Published: June 2004

AbstractNew parametric and non‐parametric identification techniques, based on wavelet expansion, for dynamic systems is shown. The identification results of the parameters of models obtained by the least‐squares method using the Haar wavelet packet analysis of randomly disturbed displacement signal is presented. New differentiation procedure of the measured data exploiting the properties of the wavelet packet analysis of a signal is applied. The non‐parametric identification results of models are known in the form of the restoring force surfaces.
Experimental Identification of a Surface Delamination of a Laminated Sandwich Beam
Authors: Müller I. , Schmieg H. 
Published: June 2004

AbstractThe oscillation properties of a laminate structure yields information about its structural integrity. Unilateral constraints and impacts dominate the oscillation properties of delaminated structures. These phenomena give rise to a nonlinear system response, whereas the degree of the nonlinearity augments with increasing intensity of excitation. The distribution of the nonlinearity on various test points allows the localisation of a delamination, exemplarily shown here on a laminated beam with a surface delamination.
Estimation of Partial Frequency Response Functions of Periodic Time‐Variant Systems under Broadband Excitation
Authors: Prothmann Thorsten 
Published: June 2004

AbstractMechanical systems, which are described by linear periodic time‐variant differential equations, show essential differences in their dynamic behaviour compared to systems, which are described by linear time‐invariant differential equations. In case of time‐invariant systems the dynamic behaviour in the frequency domain is uncorrelated, i.e. a harmonic excitation at one frequency yields a system response at the respective frequency. Opposite to that periodic systems respond not only with the excitation frequency but also with additional side bands shifted by multiples of the parameter frequency. Thus the dynamic behaviour of periodic systems is correlated in the frequency domain, i.e. the frequency response functions (FRFs) in terms of commonly considered time‐invariant mechanical systems depend on the excitation configuration. Therefore unique partial FRFs are defined, which are independent from the excitation configuration. An estimator for the partial FRFs is introduced, which represents a decisive extension of the possibilities of experimental testing of linear periodic systems.
Dedicated analytical formulation for an experimental set‐up to determine thermomechanical properties ‐ sensitivity and inverse analyses
Authors: Wawrzynek A. , Bartoszek M. , Delpak R. , Ching‐Wen Hu. 
Published: June 2004

AbstractComputational analysis of new experiment is presented here. It is realized within two main tasks: 1. an application of inverse thermal analysis supported by thermovision measurements into evaluation of thermomechanical parameters of non‐homogeneous materials (like concrete), 2. an application of sensitivity analysis in a new experiment design process.
Dissipation of vortices in CFD‐simulations
Authors: Krieger Michael , Wimmer Peter 
Published: June 2004

AbstractThe aim of this investigation is to find out the crucial factors for the meshing of a wing and especially the area behind the wingtip with the intention to keep numerical vortex‐dissipation low to be able to analyse the trailing edge vortices of the wing in inviscid CFD‐simulations. In a series of basic test‐simulations spatial vortex propagation is observed for different cell types, mesh sizes and vorticities. A numerical viscosity is determined by comparing numerical results with an analytical solution for vortex‐decay. The information gained is applied to a numerical analysis of a trailing edge vortex of a rectangular wing. The results of the numerical calculations are compared to PIV‐measurements of trailing edge vortices and analytic results of linear wing theory.
Simulation of flow and mass transport in a meander micro‐channel subject to electroosmotic driving
Authors: Barz Dominik P.J. , Ehrhard Peter 
Published: June 2004

AbstractThe aim of this work is the investigation of the flow and mass transport in a meander micro‐channel caused by pressure and electroosmotic forces. Two‐dimensional, time dependent Finite Element simulations are employed to obtain information about the suitability of the structure for electrophoretic separation. Analytical solutions valid within the electrical double layers are asymptotically matched to the numerical solution of the core flow. The electroosmotic flow is realized for two idealized and two realistic electrical fields and the results are compared with the pressure‐driven case. The different driving methods lead to different velocity profiles and thus to different concentration profiles of a sample plug. We find that for the most of the electroosmotically‐driven cases complex flow fields with recirculation regions are present. These recirculation regions increase dispersion of the sample plug. According to the simulation results, we conclude that an improvement of the channel geometry for this electroosmotically‐driven device is needed.
Blow‐up phenomena in marginally separated boundary layer type flows
Authors: Braun S. , Kluwick A. 
Published: June 2004

AbstractIt is well‐known that unsteady effects may lead to finite time break‐down of the solutions to the fundamental equation following from the interaction theory of marginal separation which describes e.g. the leading edge flow of a slender airfoil at a small angle of attack. Recent studies dealing with the analysis of a bifurcation problem associated with this integral equation which arises if the angle of attack reaches a critical value showed that this equation can be simplified significantly for small deviations from this limiting value. The resulting evolution equation is a nonlinear partial differential equation whose local blow‐up behaviour is analyzed in detail. The existence of singular travelling waves strongly suggests the possible continuation of the solution beyond the blow‐up time.
Numerical Investigation of the Reorientation of a Free Liquid Interface upon Step Reduction in Gravity
Authors: Gerstmann J. , Michaelis M. , Dreyer M. , Rath H.J. 
Published: June 2004

AbstractIn this study we consider numerically the natural frequencies of a free liquid interface in a partly filled right circular cylinder at microgravity conditions. The dependence on the static contact angle, the fill height ratio and the boundary condition at the contact line was investigated. A formula for the calculation of the natural frequency is provided.
On a new form of marginal separation
Authors: Kinell Mats , Kluwick Alfred 
Published: June 2004

AbstractIncompressible high Reynolds number flows past a slender airfoil have the distinguishing property that there exists a critical value of the angle of attack where the wall shear stress on the suction side vanishes in a single point but immediately recovers. This phenomenon is now commonly refered to as marginal separation. In the present study it is shown that a laminar boundary layer on a flat plate subjected to a linearly retarded external flow may experience a similar behaviour if the molecular complexity of the medium is sufficiently large. The role of the critical angle of attack is played by the critical value of the freestream density ρc∞ on a given isentrope. As in the case of a slender airfoil it is possible to construct an asymptotic theory which allows to calculate small separation bubbles which form if ρ∞ becomes smaller than ρc∞.
Shear stress on the surface of a circular cylinder at rest in a moving fluid in axially symmetric flow using the Padé approximation technique
Authors: Redmond Brendan , Spillane Sandra 
Published: June 2004

AbstractFollowing the asymptotic series solution of Seban & Bond [1], this paper evaluates the shear stress on the surface of a circular cylinder of radius a at rest in a fluid moving with steady velocity U0 parallel to the axis of the cylinder. The boundary layer builds up from the front of the cylinder and its thickness increases with increasing ξ, where ξ is a non‐dimensional variable representing axial distance from the front of the cylinder. The Seban & Bond solution is valid for small ξ only, near the front of the cylinder where the boundary layer thickness is small compared with a. Curle [2] extended the Seban & Bond results, thus making them valid for larger ξ. Glauert & Lighthill [3] used an asymptotic series to solve the problem in the region where ξ is large. They also used an approximate Pohlhausen method valid for small and large ξ. It is the purpose of this paper to extend the results given by the exact asymptotic series of Seban & Bond so that they are valid for both small and large ξ. This will be done using a Padé approximation technique, which will be compared with the historical results above. It will be seen that the region of validity of the series solution is extended without the need for Curle's extensive analysis and interpolation as in the other cases.
Charakterisierung von viskoelastischen Fluiden mittels Staupunktströmung und Fano‐Strömung
Authors: Wilkes C. , Gampert B. 
Published: June 2004

AbstractEs wurde ein Dehnrheomat entwickelt, mit dem es möglich ist, Dehnströmungen von Polymerlösungen nach dem Prinzip der Staupunktmethode zu untersuchen. Die Konzentration kann bei diesem Anlagentyp unterhalb der kritischen Konzentration liegen, die für die Ausbildung einer transienten Netzwerkstruktur unter Strömungsbedingungen angegeben werden kann. Mit einer weiteren Versuchsanlage, mit der nach dem Prinzip der Fano‐Strömung Dehnstr ömungen erzeugt werden können, wurden im Rahmen dieser Arbeit viskoelastische Fluide untersucht. Für die Untersuchungen wurden kommerzielle Polyacrylamide, gelöst in wässerigen Lösungsmitteln, verwendet.
A comparison of algebraic Reynolds stress models for the prediction of the turbulent flow inside a turbomachine rotor
Authors: Antonello Marco , Masi Massimo , Navarro Giampaolo 
Published: June 2004

AbstractAn algebraic Reynolds stress model has been developed and tested simulating the turbulent flow inside a centrifugal impeller. The prediction of the model are compared with those of other algebraic turbulent stress models, in order to analyse the capability of properly account for effects such as flow curvature, flow separation, and solid wall rotation.
Large‐eddy simulation of shock‐turbulence interaction with finite volumes and the Approximate Deconvolution Model
Authors: von Kaenel R. , Kleiser L. , Adams N. A. , Vos J. B. 
Published: June 2004

AbstractThe supersonic flow over a compression corner is computed by Large‐Eddy Simulation (LES) using the Approximate Deconvolution Model (ADM) and a finite volume method. Results are in excellent agreement with DNS.
Solving functions in problems of mathematical physics
Authors: Al Khatib M.J. , Grysa K. 
Published: June 2004

AbstractFor any linear partial differential equation the solving functions are such ones that satisfy the equation and form a complete set of functions. In the paper the heat polynomials (i.e. solving functions for the heat conduction equation) are discussed as a representative example. They are used to construct an approximate solution of a given problem in a form of linear combination of the polynomials.
On the Thermoregulation in the Human Microvascular System
Authors: Deuflhard Peter , Hochmuth Reinhard 
Published: June 2004

AbstractThe bio‐heat transfer equation is a macroscopic model for describing the heat transfer in microvascular tissue. So far the derivation of the Helmholtz term arising in the bio‐heat transfer equation is not completely satisfactory. Our results show that this term may be understood as asymptotic result of boundary value problems which provide a microscopic description for microvascular tissue. In view of a future integration of the bio‐heat transfer equation in a heterogeneous heat distribution model we present also asymptotic estimtates for first order correctors.
3D Particle Tracking Thermometry for Thermo‐Convective Flow Analysis
Authors: Heiland Hans Georg , Wozniak Günter 
Published: June 2004

AbstractA new optical measurement technique for the investigation of thermo‐convective flow processes is the 3D particle tracking thermometry (3D PTT). This method is based on a combination of particle tracking velocimetry and liquid crystal tracer technique. Within observation volumes in fluids velocity and temperature fields can be determined simultaneously.
Freezing and thawing at the high hydrostatic pressure conditions ‐ modelling and numerical simulation
Authors: Kowalczyk Wojciech , Hartmann Christoph , Delgado Antonio 
Published: June 2004

AbstractIn this paper the modelling and numerical simulation of the freezing and thawing processes of water under high hydrostatic pressure up to 200 MPa is presented. The system of equation consists of the conservation laws of mass, momentum and energy. Moreover, it contains also the equation of phase change and the equations of state for water and ice. In order to model the phase transitions the enthalpy‐porosity method is used. The finite‐volume method is used to solve the system of equations and to simulate different cases of phase transitions. After analysing the results from our numerical simulations it can be seen that the fluid flow in a vessel at high pressure differs from that at normal pressure. The spatial ice developing depends more strongly on convection than on conduction in larger high pressure chambers. Very good agreement between results from numerical simulation and experiment is obtained.
A Joule‐Thomson process with condensation and evaporation
Authors: Loimer Thomas 
Published: June 2004

AbstractThe one‐dimensional flow of a fluid near saturation through a porous plug is considered. Upstream of the plug, the vapor is in the state of saturation. It is assumed that (i) the vapor cools down in a throttling process and (ii) it is in the unsaturated state downstream of the plug. At the upstream surface of the plug, the saturated vapor releases heat by partial or full condensation. If the permeability of the plug lies above a critical value the vapor condenses partially, otherwise full condensation occurs and a liquid film appears in front of the plug. In a small range of permeabilities above the critical value, the vapor condenses partially at the upstream surface, then it condenses fully at a front within the plug. Consuming the heat conducted downstream, the fluid evaporates fully at an evaporation front within the plug. The value of the critical permeability is a function of thermodynamic and transport properties of the fluid and of the thermal conductivity of the plug. The values of the permeabilities where the transitions between the different types of the process occur depend on the pressure difference across the porus plug.
Numerical Simulation of Fluid Flow and Enzyme Catalysed Substrate Conversion in a Packed‐bed Enzyme Reactor
Authors: Özmutlu Ö. , Hartmann C. , Delgado A. 
Published: June 2004

AbstractThis numerical study evaluates the momentum and mass transfer in an immobilized enzyme reactor. The simulation gives detailed information of the local substrate and product concentrations with respect to external and internal transport limitations. The flow field characterization of the system makes it possible to understand fluid mechanical properties and its importance on transport processes. With the obtained data it is also possible to detect zones of high, low and latent enzymatic activity and to determine whether the conversion is limited due to mass transfer or reaction resistances.
Grid convergence in large scale reactive flow calculations
Authors: Bielert Ulrich 
Published: June 2004

AbstractNumerical simulations of turbulent combustion experiments in a large scale test facility (total length 35m) were performed solving the compressible Navier‐Stokes equations together with an k‐ϵ turbulence model and an eddybreakup combustion model. In the simulations the cell size and the model parameters of the combustion model were varied. The numerical results were compared to experimental data. The results indicate that rather coarse grids are sufficient to resolve essential features of the experiment, but user experience is required to choose good values for the model parameters.