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  • Artikel  (46)
  • finite element method  (46)
  • Wiley-Blackwell  (46)
  • Blackwell Publishing Ltd
  • 1995-1999  (46)
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  • Artikel  (46)
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  • Wiley-Blackwell  (46)
  • Blackwell Publishing Ltd
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  • 1995-1999  (46)
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  • 1
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 3 (1998), S. 229-256 
    ISSN: 1082-5010
    Schlagwort(e): finite element method ; viscous constitutive equations ; time-discrete scheme ; stability ; superstability ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: The general framework of the paper deals with the finite element modelling of mechanical problems involving viscous materials such as bitumen or bituminous concrete. Its aim is to present a second-order-accurate discrete scheme which remains unconditionally superstable when used for the time discretization of the linear and non-linear viscoelastic constitutive equations considered. After stating the space- and time-continuous mechanical problem we focus on the time discretization of these equations, considering three different schemes. For both of them sufficiently small values of the time step are required in order to ensure the superstability, whereas the third remains unconditionally superstable. Eventually, some numerical results are presented. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 26 (1998), S. 403-442 
    ISSN: 0271-2091
    Schlagwort(e): oscillating flow ; Keulegan-Carpenter number ; finite element method ; in-line force ; transverse force ; Engineering ; Numerical Methods and Modeling
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: The results of a numerical study of the viscous oscillating flow around a circular cylinder at low Keulegan-Carpenter numbers (KC) and frequency parameters (β) are presented in this paper. The finite element method was used for the solution of the Navier-Stokes equations in the formulation where the streamfunction and vorticity are the field variables. The computation was conducted at Keulegan-Carpenter numbers extending up to KC=15 and frequency parameters ranging between β=6 and 100. At low values of the Keulegan-Carpenter number the flow remains symmetrical. As the Keulegan-Carpenter number is increased over a certain value which depends also on the frequency parameter, asymmetries appear in the flow which are eventually amplified and lead finally to complex vortex-shedding patterns, some of which are markedly different from those observed at higher frequency parameters. The solution revealed that although for certain values of KC and β the shedding of vortices is periodic, there also exists a complicated flow regime in which the flow is not periodic but switches between different modes in consecutive cycles of flow oscillation. For the various flow cases examined, the traces of the hydrodynamic forces are presented and the hydrodynamic coefficients and RMS values of the in-line force are compared with experimental evidence. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 33 Ill.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 26 (1998), S. 677-696 
    ISSN: 0271-2091
    Schlagwort(e): second-order closure model ; pollutant dispersion ; finite element method ; unstably stratified atmosphere ; parallel computation ; Engineering ; Numerical Methods and Modeling
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: Pollutant dispersion under unstably stratified atmosphere was investigated numerically using the finite element method. The effects of atmospheric stability on plume trajectory were studied using a three-dimensional second-order closure dispersion model. The numerical model was implemented using domain decomposition method and carried out using a parallel computer. The computation accelerates significantly and the size of computation can be largely increased as a result of the parallelism. A passive contaminant point source was placed at the middle of the convective boundary layer to simulate the atmospheric dispersion. The requirement of the input of dispersion coefficients in k-theory and Gaussian models was replaced with direct input of turbulence flow data. It was found that the present numerical model can predict several non-Gaussian plume behaviours and the computed results agreed well with findings from experimental observations. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 28 (1998), S. 143-156 
    ISSN: 0271-2091
    Schlagwort(e): turbine ; spiral casing ; finite element method ; Galerkin weighted residual technique ; Gauss-Legendre quadrature ; Engineering ; Numerical Methods and Modeling
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: Flow through the spiral casing of a hydraulic turbine was analyzed. Reynolds averaged Navier-Stokes equations were solved using a finite element method. The physical domain was divided into a number of hexahedral elements which are isoparametrically mapped onto standard cubic elements. Numerical integration for the unsteady momentum equation is performed over such hexahedral elements to obtain a provisional velocity field. Compliance with the mass conservation equation and determination of the pressure correction are accomplished through an iterative procedure. The velocity distribution inside the spiral casing corroborates the results available in literature. The static pressure at the midplane generally decreases from the outside wall towards the exit of the spiral casing. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 28 (1998), S. 461-476 
    ISSN: 0271-2091
    Schlagwort(e): advection-diffusion equation ; operator splitting algorithm ; Holly and Preissmann scheme ; method of characteristics ; finite element method ; Engineering ; Numerical Methods and Modeling
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: Operator splitting algorithms are frequently used for solving the advection-diffusion equation, especially to deal with advection dominated transport problems. In this paper an operator splitting algorithm for the three-dimensional advection-diffusion equation is presented. The algorithm represents a second-order-accurate adaptation of the Holly and Preissmann scheme for three-dimensional problems. The governing equation is split into an advection equation and a diffusion equation, and they are solved by a backward method of characteristics and a finite element method, respectively. The Hermite interpolation function is used for interpolation of concentration in the advection step. The spatial gradients of concentration in the Hermite interpolation are obtained by solving equations for concentration gradients in the advection step. To make the composite algorithm efficient, only three equations for first-order concentration derivatives are solved in the diffusion step of computation. The higher-order spatial concentration gradients, necessary to advance the solution in a computational cycle, are obtained by numerical differentiations based on the available information. The simulation characteristics and accuracy of the proposed algorithm are demonstrated by several advection dominated transport problems. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 133-149 
    ISSN: 0363-9061
    Schlagwort(e): thermoporoelasticity ; thermoporoplasticity ; Laplace transform ; Stehfest algorithm ; finite element method ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: Solutions are presented for the behaviour of a layered porous space which contains a decaying heat source. Such a problem arises when high-level nuclear waste is placed in deep underground depositories in deep clayey formations of sedimentary basins. The geometry of the problem is one dimensional and the porous space is constituted by two layers: a deep low permeability layer which contains the nuclear waste disposal and a superficial layer. The solution is used to examine the effects of contrasts of permeability, thermal conductivity and specific heat capacities between the two layers on the large-scale behaviour of the porous space. Results are presented, using realistic data, for the pore pressure and temperature evolution at the heat source centre, and for the vertical displacement of the ground level. The superficial layer has no significant effects on pore pressure, temperature and stress evolution near the heat source centre. The vertical displacement of the ground level is mainly due to the thermal dilatation of the pore water, so it decreases with an increasing of permeability of the superficial layer. The solution of the time-dependent problem is carried out by applying Laplace transforms to the field variables, obtaining solutions and then using numerical methods to invert the transformed solutions. Comparisons with numerical simulations taking into account the non-linear and non-reversible behaviour of the rock mass are presented. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 245-261 
    ISSN: 0363-9061
    Schlagwort(e): Cosserat continuum model ; equivalent continuum medium ; layered rock mass ; finite element method ; non-associative plasticity ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: Layered rock masses can be modelled either as standard, orthotropic continua if the layer bending can be neglected or as Cosserat continua if the influence of layer bending is essential. This paper presents a finite element smeared joint model based on the Cosserat theory. The layers are assumed to be elastic with equal thickness and equal mechanical properties. All the cosserat parameters are expressed through the elastic properties of layers, layer thickness and joint stiffness. Plastic-slip as well as tensile-opening of layer interface (joint) are accounted for in a manner similar to the conventional non-associative plasticity theory.As an application, the behaviour of an excavation in a layered rock mass is examined. The displacement and stress fields given by smeared joint models based on the Cosserat continuum and the conventional anisotropic continuum approaches are compared with those obtained from the discrete joint model. The conventional anisotropic continuum model is found to break-down completely when the effective shear modulus in the direction parallel to layering is low in comparison to the shear modulus of the intact layer, whereas the Cosserat model is found to be capable of accurately reproducing complex load-deflection patterns irrespective of the differences in shear moduli. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 26 (1998), S. 1127-1154 
    ISSN: 0271-2091
    Schlagwort(e): free surface ; transient viscous incompressible fluid ; finite element method ; VOF (volume-of-fluid) method ; adaptive grid ; Engineering ; Numerical Methods and Modeling
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: The VOF method is adopted for the finite element analysis of transient fluid flow with a free surface. In particular, an adaptation technique for generating an adaptive grid is incorporated to capture a higher resolution of the free surface configuration. An adaptive grid is created through the refinement and mergence of elements. In this domain the elements in the surface region are made finer than those in the remaining regions for more efficient computation. Also, three techniques based on the VOF method are newly developed to increase the accuracy of the analysis, namely the filling pattern, advection treatment and free surface smoothing techniques. Using the proposed numerical techniques, radial flow with a point source and the collapse of a dam are analysed. The numerical results agree well with the theoretical solutions as well as with the experimental results. Through comparisons with the numerical results of several cases using different grids, the efficiency of the proposed technique is verified. © 1998 by John Wiley & Sons, Ltd.
    Zusätzliches Material: 28 Ill.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 27 (1998), S. 159-168 
    ISSN: 0271-2091
    Schlagwort(e): finite element method ; Galerkin method ; residual free bubbles ; Engineering ; Numerical Methods and Modeling
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: An overview of the unusual stabilized finite element method and of the standard Galerkin method enriched with residual free bubble functions is presented. For the first method a concrete model problem illustrates its application in advective-diffusive-reactive equations and for the second method it is shown how static condensation of residual free bubbles gives rise to mass lumping and selective reduced integration, which are viewed as numerical tricks and can now be derived by the standard Galerkin method without tricks. © 1998 John Wiley & Sons, Ltd.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 27 (1998), S. 139-157 
    ISSN: 0271-2091
    Schlagwort(e): hydrodynamic stability ; finite element method ; incompressible cavity flow ; Arnold's method ; Engineering ; Numerical Methods and Modeling
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: Numerical methods have been applied to theoretical studies of instability and transition to turbulence. In this study an analysis of the linear stability of incompressible flow is undertaken. By means of the finite element method the two-dimensional base flow is computed numerically over a range of Reynolds numbers and is perturbed with three-dimensional disturbances. The partial differential equations governing the evolution of perturbation are obtained from the non-linear Navier-Stokes equations with a slight compressibility by using linear stability and normal mode analysis. In terms of the finite element discretization a non-singular generalized eigenproblem is formulated from these equations whose solution gives the dispersion relation between complex growth rate and wave number. This study presents stability curves to identify the critical Reynolds number and critical wavelength of the neutral mode and discusses the mechanism of instability. The stability of lid-driven cavity flow is examined. Taylor-Göertler-like vortices in the cavity are obtained by means of reconstruction of three-dimensional flows. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
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  • 11
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 28 (1998), S. 95-112 
    ISSN: 0271-2091
    Schlagwort(e): square columns in tandem ; finite element method ; improved BTD ; 3D computation ; aerodynamic characteristics ; Engineering ; Numerical Methods and Modeling
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: Two- (2D) and three-dimensional (3D) finite element analyses for flow around two square columns in tandem arrangement were performed with various column spacings and Reynolds numbers. The computed values were compared with the wind-tunnel results in terms of the aerodynamic characteristics of the leeward column. In most 2D computations, strong vortices were formed behind the windward column, irrespective of widely changed Reynolds numbers. This was different from the experimental phenomena of equivalent spacing, so that the computed time-averaged pressure coefficients were not identical to the experimental values except when the distance between the two columns was adequately wide or narrow. On the other hand, in 3D computation, distinct differences in flow structures behind the column were observed between Reynolds numbers of 103 and 104 and the pressure coefficient in the 3D analysis with Re=104 agreed well with the experimental value. Thus, the effectiveness of 3D computations and Reynolds number effects on the flow around two square columns have been confirmed. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 17 Ill.
    Materialart: Digitale Medien
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  • 12
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 28 (1998), S. 719-736 
    ISSN: 0271-2091
    Schlagwort(e): front tracking ; mesh adaptation ; finite element method ; Engineering ; Numerical Methods and Modeling
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: A numerical model is developed for the simulation of moving interfaces in viscous incompressible flows. The model is based on the finite element method with a pseudo-concentration technique to track the front. Since a Eulerian approach is chosen, the interface is advected by the flow through a fixed mesh. Therefore, material discontinuity across the interface cannot be described accurately. To remedy this problem, the model has been supplemented with a local mesh adaptation technique. This latter consists in updating the mesh at each time step to the interface position, such that element boundaries lie along the front. It has been implemented for unstructured triangular finite element meshes. The outcome of this technique is that it allows an accurate treatment of material discontinuity across the interface and, if necessary, a modelling of interface phenomena such as surface tension by using specific boundary elements. For illustration, two examples are computed and presented in this paper: the broken dam problem and the Rayleigh-Taylor instability. Good agreement has been obtained in the comparison of the numerical results with theory or available experimental data. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
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  • 13
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 28 (1998), S. 1355-1369 
    ISSN: 0271-2091
    Schlagwort(e): viscous flow ; moving boundary ; fountain flow ; pseudo-concentration method ; finite element method ; Engineering ; Numerical Methods and Modeling
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: Mould filling processes, in which a material flow front advances through a mould, are typical examples of moving boundary problems. The moving boundary is accompanied by a moving contact line at the mould walls causing, from a macroscopic modelling viewpoint, a stress singularity. In order to be able to simulate such processes, the moving boundary and moving contact line problem must be overcome. A numerical model for both two- and three-dimensional mould filling simulations has been developed. It employs a pseudo-concentration method in order to avoid elaborate three-dimensional remeshing, and has been implemented in a finite element program. The moving contact line problem has been overcome by employing a Robin boundary condition at the mould walls, which can be turned into a Dirichlet (no-slip) or a Neumann (free-slip) boundary condition depending on the local pseudo-concentration. Simulation results for two-dimensional test cases demonstrate the model's ability to deal with flow phenomena such as fountain flow and flow in bifurcations. The method is by no means limited to two-dimensional flows, as is shown by a pilot simulation for a simple three-dimensional mould. The reverse problem of mould filling is the displacement of a viscous fluid in a tube by a less viscous fluid, which has had considerable attention since the 1960's. Simulation results for this problem are in good agreement with results from the literature. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 14
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 27 (1998), S. 109-125 
    ISSN: 0271-2091
    Schlagwort(e): multiphase porous material ; cavitation ; water pressure ; vapour pressure ; strain localization ; finite element method ; Engineering ; Numerical Methods and Modeling
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: A model to simulate cavitation phenomena in the pores of saturated porous media is developed. Such phenomena appear in connection with pore water traction, which may be observed during strain localization in dense sand samples or in dynamic fluid-structure interaction problems where the structure is made of geomaterials. The model makes use of an isothermal two-phase flow approach. Numerical examples relating to strain localization are shown. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 15
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 28 (1998), S. 633-661 
    ISSN: 0271-2091
    Schlagwort(e): free convection ; porous enclosure ; Darcian model ; wavy surface ; finite element method ; numerical study ; Engineering ; Numerical Methods and Modeling
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: The coupled streamfuction-temperature equations governing the Darcian flow and convection process in a fluid-saturated porous enclosure with an isothermal sinusoidal bottom sun face, has been numerically analyzed using a finite element method (FEM). No restrictions have been imposed on the geometrical non-linearity arising from the parameters like wave amplitude (a), number of waves per unit length (N), wave phase (Φ), aspect ratio (A) and also on the flow driving parameter Rayleigh number (Ra). The numerical simulations for varying values of Ra bring about interesting flow features, like the transformation of a unicellular flow to a multicellular flow. Both with increasing amplitude and increasing number of waves per unit length, owing to the shift in the separation and reattachment points, a row-column pattern of multicellular flow transforms to a simple row of multicellular flow. A cycle of n celluar and n+1 cellular flows, with the flow in adjacent cells in the opposite direction, periodically manifest with phase varying between 0 and 360°. The global heat transfer into the system has been found to decrease with increasing amplitude and increasing number of waves per unit length. Only marginal changes in the global heat flux are observed, either with increasing Ra or varying Φ. Effectively, sinusoidal bottom surface undulations of the isothermal wall of a porous enclosure reduces the heat transfer into the system. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 21 Ill.
    Materialart: Digitale Medien
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  • 16
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 25 (1997), S. 205-223 
    ISSN: 0271-2091
    Schlagwort(e): optimal control ; Navier-Stokes equations ; finite element method ; Engineering ; Numerical Methods and Modeling
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: We study the numerical solution of optimal control problems associated with two-dimensional viscous incompressible thermally convective flows. Although the techniques apply to more general settings, the presentation is confined to the objectives of minimizing the vorticity in the steady state case and tracking the velocity field in the non-stationary case with boundary temperature controls. In the steady state case we develop a systematic way to use the Lagrange multiplier rules to derive an optimality system of equations from which an optimal solution can be computed; finite element methods are used to find approximate solutions for the optimality system of equations. In the time-dependent case a piecewise-in-time optimal control approach is proposed and the fully discrete approximation algorithm for solving the piecewise optimal control problem is defined. Numerical results are presented for both the steady state and time-dependent optimal control problems. © 1997 John Wiley & Sons, Ltd.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 17
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 25 (1997), S. 371-392 
    ISSN: 0271-2091
    Schlagwort(e): adaptive grids ; finite element method ; iterative solvers ; Engineering ; Numerical Methods and Modeling
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: This paper presents the development of the three- dimensional prolonged adaptive finite element equation solver for the Navier-Stokes equations. The finite element used is the tetrahedron with quadratic approximation of the velocities and linear approximation of the pressure. The equation system is formulated in the basic variables. The grid is adapted to the solution by the element Reynolds number. An element in the grid is refined when the Reynolds number of the element exceeds a preset limit. The global Reynolds number in the investigation is increased by scaling the solution for a lower Reynolds number. The grid is refined according to the scaled solution and the prolonged solution for the lower Reynolds number constitutes the start vector for the higher Reynolds number. Since the Reynolds number is the ratio of convection to diffusion, the grid refinements act as linearization and symmetrization of the equation system. The linear equation system of the Newton formulation is solved by CGSTAB with coupled node fill-in preconditioner. The test problem considered is the three-dimensional driven cavity flow. © 1997 John Wiley & Sons, Ltd.
    Zusätzliches Material: 17 Ill.
    Materialart: Digitale Medien
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  • 18
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 25 (1997), S. 495-512 
    ISSN: 0271-2091
    Schlagwort(e): separated flows ; recirculation length ; finite element method ; Engineering ; Numerical Methods and Modeling
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: The incompressible, laminar, isothermal flow of a Newtonian fluid at steady state past a surface-mounted obstacle (flow over a step) is studied in a two-dimensional numerical experiment using the Galerkin finite element method. The dimensionless Navier-Stokes equations are solved in the whole range of the laminar flow regime. The numerical predictions are compared with available experimental data. The emphasis in the discussion of the results is on the presentation of the streamlines for various Reynolds numbers, the pressure distribution over and downstream of the step, the shear stress distribution along the surface of the step and the length of the recirculation region as a function of the Reynolds number. This analysis may be used in numerous applications from agricultural to civil, mechanical and chemical engineering. © 1997 John Wiley & Sons, Ltd.
    Zusätzliches Material: 22 Ill.
    Materialart: Digitale Medien
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  • 19
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 24 (1997), S. 965-986 
    ISSN: 0271-2091
    Schlagwort(e): turbulence models ; k-ε ; non-linear k-ε ; finite element method ; validation ; FEAT ; Engineering ; Numerical Methods and Modeling
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: Standard, modified and non-linear k-ε: turbulence models are validated against three axisymmetric flow problems - flow through a pipe expansion, flow through a pipe constriction and an impinging jet problem - to underpin knowledge about the solution quality obtained from two-equation turbulence models. The extended models improve the prediction of turbulence as a flow approaches a stagnation point and the non-linear model allows for the prediction of anisotropic turbulence. Significantly different values for the non-linear model coefficients are proposed in comparison with values found in the literature. Nevertheless, current turbulence models are still unable to accurately predict the spreading rate of shear layers. © 1997 by John Wiley & Sons, Ltd. Int. j. numer. methods fluids, 24: 965-986, 1997.
    Zusätzliches Material: 21 Ill.
    Materialart: Digitale Medien
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  • 20
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 21 (1997), S. 485-494 
    ISSN: 0363-9061
    Schlagwort(e): finite element method ; ground water ; phreatic surface ; transient flow ; unconfined seepage ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: Peformance of rectangular trench drains penetrating fully in a layer of homogeneous and isotropic soil mass down to an underlying impervious base with time has been assessed using the finite element method. Non-dimensional charts have been developed comprehensively to establish the successive positions of a phreatic surface with the passage of time for any given values of permeability of soil and its specific yield. The effect of spacing to depth ratios of drains on their performance has been examined in detail. The rate of downward movements of the phreatic surface decreases with time as well as with increases in the spacing of drains. The spacing affects considerably the magnitudes of drawdown at distant locations from the drains, whereas close to the drains, its effect becomes insignificant. © 1997 John Wiley & Sons, Ltd.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 21
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 21 (1997), S. 199-225 
    ISSN: 0363-9061
    Schlagwort(e): nuclear waste disposed ; numerical analysis ; finite element method ; thermohydromechanics ; saturated porous media ; temperature effect ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: The theoretical aspects of fully coupled thermohydromechanical behaviour of saturated porous media are presented. The non-linear behaviour of soil skeleton is assumed. A new concept called ‘thermal void ratio state surface’ is introduced to include thermal effects, and the stress state level influence on volume changes. The fluid phase flows according to Darcy's law and energy transport is assumed to follow Fourier's law classically. Variation of water permeability, water and solid unit weight due to thermal effects and pore pressure changes are included. A finite element package is developed based on final matrix form obtained from discretization of integral form of field equations by finite element method and integration in time. A very good agreement between the theoretical predictions and the experimental results was obtained for the several simple problems proposed by other authors. © 1997 by John Wiley & Sons, Ltd.
    Zusätzliches Material: 13 Ill.
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  • 22
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 21 (1997), S. 599-618 
    ISSN: 0363-9061
    Schlagwort(e): embankments ; finite element method ; ground improvement ; settlements ; soft clay ; vertical drains ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: In 1986, the Malaysian Highway Authority constructed a series of trial embankments on the Muar Plain (soft marine clay) with the aim of evaluating the effectiveness of various ground improvement techniques. This study investigates the effect of two such ground improvement schemes: (a) preloading of foundation with surface geogrids and synthetic vertical drains and (b) sand compaction piles. The paper is focused on the finite element analysis of settlements and lateral displacements of the soft foundation. In scheme (a), the numerical predictions are compared with the field measurements. In scheme (b), only the numerical analysis is presented and discussed in the absence of reliable measurements due to the malfunctioning of the electronic extensometer and inclinometer system during embankment construction. The current analysis employs critical state soil mechanics, and the deformations are predicted on the basis of the fully coupled (Biot) consolidation model. The vertical drain pattern is converted to equivalent drain walls to enable plane strain modelling, and the geogrids are simulated by linear interface slip elements. The effect of sand compaction piles is investigated considering both ideal drains and non-ideal drains, as well as varying the pile stiffness. © 1997 by John Wiley & Sons, Ltd.
    Zusätzliches Material: 16 Ill.
    Materialart: Digitale Medien
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  • 23
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 24 (1997), S. 615-638 
    ISSN: 0271-2091
    Schlagwort(e): finite element method ; front tracking ; incompressible two fluid system ; mold filling ; Engineering ; Numerical Methods and Modeling
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: A numerical model has been developed for the 2D simulation of free surface flows or, more generally speaking, moving interface ones. The bulk fluids on both sides of the interface are taken into account in simulating the incompressible laminar flow state. In the case of heat transfer the whole system, i.e. walls as well as possible obstacles, is considered. This model is based on finite element analysis with an Eulerian approach and an unstructured fixed mesh. A special technique to localize the interface allows its temporal evolution through this mesh. Several numerical examples are presented to demonstrate the capabilities of the model. © 1997 by John Wiley & Sons, Ltd.
    Zusätzliches Material: 22 Ill.
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  • 24
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 24 (1997), S. 953-963 
    ISSN: 0271-2091
    Schlagwort(e): coastal hydrodynamics ; shallow water equations ; finite element method ; finite difference method ; Engineering ; Numerical Methods and Modeling
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: This paper presents the results of some studies on the development and application of a finite element method (FEM) with a closed-form solution technique for time discretization. The closed-form solution is based on the eigenvalues/vectors of a coefficient matrix. The method is first applied to the one-dimensional linearized shallow water equations and then extended to the two-dimensional shallow water equations. An attempt is made to improve its efficiency by incorporating time splitting and using the closed-form solution technique only for linear terms. Some case studies of a rectangular channel and harbour are presented to illustrate the satisfactory working of the method. © 1997 by John Wiley & Sons, Ltd. Int. j. numer. methods fluids 24: 953-963, 1997.
    Zusätzliches Material: 12 Ill.
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  • 25
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 25 (1997), S. 1421-1454 
    ISSN: 0271-2091
    Schlagwort(e): incompressible Navier-Stokes problem ; finite element method ; high-order time scheme ; method of characteristics ; Engineering ; Numerical Methods and Modeling
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: In this paper we consider a discretization of the incompressible Navier-Stokes equations involving a second-order time scheme based on the characteristics method and a spatial discretization of finite element type. Theoretical and numerical analyses are detailed and we obtain stability results abnd optimal eror estimates on the velocity and pressure under a time step restriction less stringent than the standard Courant-Freidrichs-Levy condition. Finally, some numerical results obtained wiht the code N3S are shown which justify the interest of this scheme and its advantages with respect to an analogous first-order time scheme. © 1997 John Wiley & Sons, Ltd.
    Zusätzliches Material: 8 Ill.
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  • 26
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 25 (1997), S. 719-736 
    ISSN: 0271-2091
    Schlagwort(e): finite element method ; fictitious domain method ; three-dimensional ; internal parts ; incompressible fluid flow ; constrained optimization ; Engineering ; Numerical Methods and Modeling
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: A new Galerkin finite element method for the solution of the Navier-Stokes equations in enclosures containing internal parts which may be moving is presented. Dubbed the virtual finite element method, it is based upon optimization techniques and belongs to the class of fictitious domain methods. Only one volumetric mesh representing the enclosure without its internal parts needs to be generated. These are rather discretized using control points on which kinematic constraints are enforced and introduced into the mathematical formulation by means of Lagrange multipliers. Consequently, the meshing of the computational domain is much easier than with classical finite element approaches.   First, the methodology will be presented in detail. It will then be validated in the case of the two-dimensional Couette cylinder problem for which an analytical solution is available. Finally, the three-dimensional fluid flow inside a mechanically agitated vessel will be investigated. The accuracy of the numerical results will be assessed through a comparison with experimental data and results obtained with a standard finite element method. © 1997 John Wiley & Sons, Ltd.
    Zusätzliches Material: 13 Ill.
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  • 27
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 25 (1997), S. 779-802 
    ISSN: 0271-2091
    Schlagwort(e): finite element method ; vertical velocity ; three-dimensional ; Vancouver Island ; Engineering ; Numerical Methods and Modeling
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: Computation of vertical velocity within the confines of a three-dimensional, finite element model is a difficult but important task. This paper examines four approaches to the solution of the overdetermined system of equations arising when the first-order continuity equation is solved in conjunction with two boundary conditions. The traditional (TRAD) method neglects one boundary condition, solving the continuity equation with the remaining boundary condition. The vertical derivative of continuity (VDC) method involves solution of the second-order equation obtained by differentiation of the continuity equation with respect to the vertical co-ordinate. The least squares (LS) method minimizes the residuals of the continuity equation (in discrete form) and the two boundary conditions. The adjoint (ADJ) method minimizes the residuals of the continuity equation (in continuous form) and the two boundary conditions.Two domains are considered: a quarter-annular harbour and the southwest coast of Vancouver Island. Results indicate that the highest-quality solution is obtained with both LS and ADJ. Furthermore, ADJ requires less CPU and memory than LS. Therefore the optimal method for computation of vertical velocity in a three-dimensional finite element model is the adjoint (ADJ) method. © 1997 John Wiley & Sons, Ltd.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
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  • 28
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 25 (1997), S. 847-857 
    ISSN: 0271-2091
    Schlagwort(e): finite element method ; blood flow ; arterial transport processes ; curved tubes ; Engineering ; Numerical Methods and Modeling
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: A numerical scheme for the simulation of blood flow and transport processes in large arteries is presented. Blood flow is described by the unsteady 3D incompressible Navier-Stokes equations for Newtonian fluids; solute transport is modelled by the advection-diffusion equation. The resistance of the arterial wall to transmural transport is described by a shear-dependent wall permeability model. The finite element formulation of the Navier-Stokes equations is based on an operator-splitting method and implicit time discretization. The streamline upwind/Petrov-Galerkin (SUPG) method is applied for stabilization of the advective terms in the transport equation and in the flow equations. A numerical simulation is carried out for pulsatile mass transport in a 3D arterial bend to demonstrate the influence of arterial flow patterns on wall permeability characteristics and transmural mass transfer. The main result is a substantial wall flux reduction at the inner side of the curved region. © 1997 John Wiley & Sons, Ltd.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 29
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 25 (1997), S. 931-952 
    ISSN: 0271-2091
    Schlagwort(e): finite element method ; free surface ; updated Lagrangian-Eulerian ; Engineering ; Numerical Methods and Modeling
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: An updated free surface Lagrangian-Eulerian finite element kinematic description is used to simulate free surface flow problems associated with mould filling. The method proposed results in an accurate determination of the front, making it ideal for problems in which free surface boundary conditions play an important role. Significant saving in CPU time can be obtained over other fixed mesh approaches by virtue of the air domain being ignored. Assuming a laminar regime for the flow field, a mixed interpolation formulation is used to approximate the discretized governing equations for elimination.   Of particular interest is the method implementation to restrict the number of remeshing operations and track the moving free surface within an arbitrary domain, either with or without internal obstacles. The method used to automatically assign boundary conditions to the changing domain is described. A dam break problem is modelled numerically and compared against experimentally derived data in order to validate the model. A further numerical example demonstrates the capabilities of the algorithm developed to model the filling of an industrial casting. © 1997 John Wiley & Sons, Ltd.
    Zusätzliches Material: 23 Ill.
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  • 30
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996), S. 95-114 
    ISSN: 1082-5010
    Schlagwort(e): multiphase material ; strain localisation ; averaging theories ; pore pressure ; cavitation ; finite element method ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: It is recalled that negative water pressures are of importance in localisation phenomena of fully saturated, undrained samples of dilatant geomaterials. A model to simulate cavitation phenomena connected with such pore water tractions is developed and implemented in a simplified form in a dynamics code for partially saturated porous media. A case of localisation is studied from the onset of the instability up to the full developed shear band. The weak mesh dependence of the maximum effective plastic strain, due to the employed physical model, is also shown.
    Zusätzliches Material: 21 Ill.
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  • 31
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 22 (1996), S. 43-66 
    ISSN: 0271-2091
    Schlagwort(e): multiple-level model ; finite element method ; open boundary condition ; tidal current analysis ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: The results of a research project to verify the newly improved multiple- level model for 3D tidal current analysis in Tokyo Bay are presented. The improved multiple-level model includes additional effects due to Coriolis force, river inflows and wind shear stresses. Furthermore, a new numerical treatment of the open boundary condition was applied which effectively eliminated the spurious reflective waves often generated by various numerical methods simulating free surface flows. The mean (time-averaged or residual) and tidal currents in Tokyo Bay were simulated as examples to demonstrate the validity and capability of the newly improved multiple-level model. A series of numerical experiments was conducted to carefully examine the tidal circulations affected by the forcing factors of Coriolis force, river inflows and wind shears, both individually and combined. The numerical results demonstrated that the effects of each forcing term are physically reasonable, with the wind shear effect being the most significant and the case including all forcing terms being in best overall agreement with the field data collected in Tokyo Bay by the Ministry of Transportation. This study has contributed not only to the verification of the newly improved multiple-level model but also to the enhancement of the accuracy of numerical simulations of three-dimensional flow in coastal waters by this model.
    Zusätzliches Material: 22 Ill.
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  • 32
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 22 (1996), S. 175-194 
    ISSN: 0271-2091
    Schlagwort(e): free-surface flow ; viscous incompressible fluid ; finite element method ; marker particle method ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: A numerical method based on the finite element method is presented for simulating the two-dimensional transient motion of a viscous liquid with free surfaces. For ease of numerical treatment of the free surface expressed by a multiple-valued function, the marker particle method is employed. Numerous virtual particles are spread over all regions occupied by liquid. They move about on a fixed finite element mesh with the liquid velocity at their positions. These particles contribute nothing to the dynamics of the liquid and only serve as markers of liquid regions. The velocity field within liquid regions is calculated by solving the Navier- Stokes equations and the equation of continuity by the finite element method based on quadrilateral elements. A detailed discussion is given of the methodological problems arising in the implementation of the marker particle method on an unstructured finite element mesh and of the solutions to these problems. The proposed method is demonstrated on three sample problems: the broken dam problem, the impact of a falling liquid drop on a still liquid and the entry of a rigid block into water. Good agreement has been obtained in the comparison of the present numerical results with available experimental data.
    Zusätzliches Material: 17 Ill.
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  • 33
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 23 (1996), S. 673-690 
    ISSN: 0271-2091
    Schlagwort(e): Euler equations ; directionally adaptive meshes ; edge-based error estimate ; structured grids ; mesh movement ; finite element method ; high-speed flows ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: The present paper describes a directionally adaptive finite element method for high-speed flows, using an edge-based error estimate on quadrilateral grids. The error of the numerical solution is estimated through its second derivatives and the resulting Hessian tensor is used to define a Riemannian metric. An improved mesh movement strategy, based on a spring analogy, but with no orthogonality constraints, is introduced to equidistribute the lengths of the edges of the elements in the defined metric. The grid adaptation procedure is validated on an analytical test case and the efficiency of the overall methodology is investigated on supersonic and hypersonic benchmarks.
    Zusätzliches Material: 21 Ill.
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  • 34
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 20 (1996), S. 865-886 
    ISSN: 0363-9061
    Schlagwort(e): finite element method ; large deformation ; cone penetration test ; layered soil ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: An Eulerean large-strain finite element formulation is presented to simulate static soil penetration. The method is an extension of the Updated Lagrangean description to an Eulerean formulation taking into account convection of deformation-history-dependent properties as well as material properties. The strength of the soil is characterized by a non-associated Drucker-Prager criterion which depends on peak and critical friction angles. The model is applied to cone penetration in two-layer systems: (a) clay on sand and (b) sand on clay.
    Zusätzliches Material: 15 Ill.
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  • 35
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 20 (1996), S. 231-252 
    ISSN: 0363-9061
    Schlagwort(e): interfaces and joints ; landslides ; viscoplastic behavior ; hierarchical single surface models ; laboratory testing ; calibration ; finite element method ; validations ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: A constitutive model to describe viscoplastic or time-dependent behaviour of interface materials is presented. Viscoplastic characteristics of the interface material are modeled based on Perzyna's theory of viscoplasticity and the Hierarchical Single Surface (HiSS) series of constitutive models. Experiments performed using a new interface test device to characterize the behaviour of cohesive soil-rock interfaces are described. Procedures to derive model parameters are presented together with validation of the model. Finite element implementation of the interface element is described along with verification of the model with respect to field behaviour of a creeping natural slope.
    Zusätzliches Material: 15 Ill.
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  • 36
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 20 (1996), S. 119-141 
    ISSN: 0363-9061
    Schlagwort(e): inverse analysis ; parameter identification ; underground excavation ; optimization technique ; finite element method ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: A probabilistic framework to perform inverse analysis of geotechnical problems is presented. The formulation allows the incorporation of existing prior information on the parameters in a consistent way. The method is based on the maximum likelihood approach that allows a straightforward introduction of the error structure of field measurements and prior information. The difficulty of ascribing definite values to the uncertainties associated with the various types of observations is overcome by including the corresponding variances in the set of parameters to be identified. The inverse analysis results in a minimization problem that is solved by coupling the optimization technique to the finite element method. Two examples are presented to illustrate the performance of the method. The first one corresponds to a synthetic case simulating the excavation of a tunnel. Young's modulus, K0 value and measurements variances are identified. The second case concerns the excavation of a large underground cavern in which again Young's modulus and K0 are identified. It is shown that introduction of prior information permits the estimation of parameters more consistent with all available informations that include not only monitored displacements but also results from in situ tests carried out during the site investigation stage.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
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  • 37
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 23 (1996), S. 163-176 
    ISSN: 0271-2091
    Schlagwort(e): convective heat transfer ; finite element method ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: The purpose of this investigation is to study the convective heat transfer from a horizontal circular cylinder under the effect of a solid plane wall. The full Navier-Stokes and energy equations for two-dimensi onal steady flow are solved by a finite element method. The variations in surface shear stress, local pressure and Nusselt number around the surface of the cylinder as well as the predicted values of average Nusselt number, location of separation and some flow and temperature fields are presented. It is found that the average Nusselt number and drag force increase as the gap between the cylinder and the wall is increased.
    Zusätzliches Material: 10 Ill.
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  • 38
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 23 (1996), S. 1197-1210 
    ISSN: 0271-2091
    Schlagwort(e): finite element method ; gust ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: In the structural design of civil aircraft the critical loads are often those encountered in a gust or atmospheric turbulence. The traditional ‘indicial’ solution is restricted to a simple plate. In this paper a finite element formulation is proposed for an aerofoil or arbitrary shape entering a uniform sharp-edged or sinusoidal gust. The thin rotational gust front and wake in an irrotational flow field are successfully modelled by a novel superposition technique. The finite element solutions are compared with the Kussner function and results by other numerical methods. The agreement is good.
    Zusätzliches Material: 16 Ill.
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  • 39
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 22 (1996), S. 429-444 
    ISSN: 0271-2091
    Schlagwort(e): modified Boussinesq equations ; finite element method ; wave-current interaction ; breaking waves ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: A two-dimensional (horizontal plane) coastal and estuarine region model, capable of predicting the combined effects of gravity surface shallow- water waves (shoaling, refraction, diffraction, reflection and breaking), and steady currents, is described and numerical results are compared with those obtained experimentally.Two series of observations within a wave flume and a combined wave-current facility were developed. In the first case, the wave was generated via a hinged paddle located within a deepened section at one end of the channel, as, in the second case, the wave propagating with or against the current was generated by a plunger-type wavemaker; the re-circulating current was introduced via one passing tank connected to a centrifugal pump.Several comparisons for a number of 1D situations and one 2D horizontal plane case are presented.
    Zusätzliches Material: 7 Ill.
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  • 40
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 20 (1995), S. 1163-1178 
    ISSN: 0271-2091
    Schlagwort(e): electrolyte flow ; finite element method ; non-linear ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: Electrical double-layer effects are unimportant in flows through porous media except when the Debye length k-1 is comparable in magnitude with the pore radius a. Under these conditions the equations governing the flow of electrolyte are those of Stokes, Nernst-Planck and Poisson. These equations are non-linear and require numerical solution. The finite element method provides a useful basis for solution and various algorithms are investigated. The numerical stability and errors of each scheme are analysed together with the development of an appropriate finite element mesh. The electro-osmotic flow of a typical electrolyte (barium chloride) through a uniformly charged cylindrical membrane pore is investigated and the ion fluxes are post-computed from the numerical solutions. The ion flux is shown to be strongly dependent on both zeta potential and pore radius, ka, indicating the effects of overlapping electrical double layers.
    Zusätzliches Material: 7 Ill.
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  • 41
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 20 (1995), S. 603-620 
    ISSN: 0271-2091
    Schlagwort(e): free surface ; free convection ; time-dependent flow ; metal flow ; finite element method ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: The finite element method is employed to investigate time-dependent liquid metal flows with free convection, free surfaces and Marangoni effects. The liquid circulates in a two-dimensional shallow trough with differentially heated vertical walls. The spatial formulation incorporates mixed Lagrangian approximations to the velocity, pressure, temperature and free surface position. The time integration is performed with the backward Euler and trapezoid rule methods with step size control. The Galerkin method is used to reduce the problem to a set of non-linear equations which are solved with the Newton-Raphson method. Calculations are performed for conditions relevant to the electron beam vaporization of refractory metals. The Prandtl number is 0·015 and Grashof number are in the transition range between laminar and turbulent flow. The results reveal the effects of flow intensity, surface tension gradients, mesh refinement and time integration strategy.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 42
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 20 (1995), S. 789-801 
    ISSN: 0271-2091
    Schlagwort(e): identification ; optimal control ; finite element method ; temperature control system ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: To avoid the use of pesticides on putting greens of golf courses, a temperature regulator system is strongly recommended nowadays in Japan. To maintain grass on the putting green without pesticide, the temperature of the ground should be controlled. This system consists of a cooling machine and buried pipes in the ground. The temperature of the water in the pipes cannot be regulated. In this paper, both identification and control problems are presented by the minimization technique and applied to a practical problem. To establish the system, it is important to obtain accurate parameters which are included in the governing equation. These parameters can be determined by parameter identification. The conjugate gradient method is used for the parameter identification procedure. The control problem aims to make the temperature at arbitrary points close to the objective temperature. The discrete-time dynamic programming is used for the control procedure.
    Zusätzliches Material: 16 Ill.
    Materialart: Digitale Medien
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  • 43
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 21 (1995), S. 973-979 
    ISSN: 0271-2091
    Schlagwort(e): finite element method ; transient flow ; power-law fluid ; extrudate swell ; marker particles ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: A simple extrusion process for Newtonian and power-law fluids is analysed. Marker particles are introduced to analyse the fluid flow motions. Area co-ordinates of six-node triangular element are used to determine the marker position in the element. With this element, the solution algorithm becomes simple compared with the one using the linear triangular element. The differences in flow and swell patterns between the two fluids are described.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 44
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 20 (1995), S. 493-506 
    ISSN: 0271-2091
    Schlagwort(e): finite element method ; mould filling ; explicit Taylor-Galerkin ; pseudo-concentration ; interface elements ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: A model for simulating the process of mould filling in castings is presented. Many defects in a casting have their origins at the filling stage. Numerical simulation of this process can be of immense practical benefit to the foundry industry, however a rigorous analysis of this process must model a wide range of complex physical phenomena. In order to contain the costs and complexity that would be necessary for such a model, certain simplifying assumptions have been made. These assumptions limit the scope of this model to only predicting realistic thermal fields during the filling process.A laminar regime has been assumed for the flow field, which is obtained by solving the incompressible Navier-Stokes equations using a velocity-pressure segregated semi-implicit finite element method. The free metal surface is predicted by advecting a pseudo-concentration function via the computed flow field. This involves an explicit finite element solution of a pure advection equation. The thermal field is calculated by solving the convective-diffusive energy equation by an explicit finite element method using the computed flow field and the location of the free surface. All the advection terms are discretized using a Taylor-Galerkin method. The interface between the metal and mould is modelled using special interface elements.The model is demonstrated by solving practical example problems. The results show that a sharp thermal front is maintained during the course of filling without excessive diffusion. The heat diffusion in the mould can be controlled by varying the metal mould heat transfer coefficient.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 45
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 21 (1995), S. 295-310 
    ISSN: 0271-2091
    Schlagwort(e): moored floating body ; finite element method ; moving boundary problem ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: The motion of a moored floating body under the action of wave forces, which is influenced by fluid forces, shape of the floating body and mooring forces, should be analysed as a complex coupled motion system. Especially under severe storm conditions or resonant motion of the floating body it is necessary to consider finite amplitude motions of the waves, the floating body and the mooring lines as well as non-linear interactions of these finite amplitude motions.The problem of a floating body has been studied on the basis of linear wave theory by many researchers. However, the finite amplitude motion under a correlated motion system has rarely been taken into account.This paper presents a numerical method for calculating the finite amplitude motion when a floating body is moored by non-linear mooring lines such as chains and cables under severe storm conditions.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 46
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 21 (1995), S. 955-966 
    ISSN: 0271-2091
    Schlagwort(e): Laplace transform ; combined method ; transient problem ; chemical reaction ; convective diffusion ; infinite region ; finite element method ; boundary element method ; coupling method ; unsteady problem ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: A numerical method for solving the problem of transient convective diffusion with a first-order chemical reaction is presented in this paper. The method is applicable over an infinite region. For steady problems the combined method of finite and boundary elements is recognized as a successful numerical technique for dealing with an infinite region. The present method is also useful in transient problems. In order to formulate the combined method for transient problems, we have developed a new method. In this paper the Laplace transform method incorporating the combined finite and boundary element methods will be considered. This transformation, holding complex values, transforms the transient problem into a steady state form. We also consider the present numerical solution which is obtained by using the numerical inverse Laplace transform as presented by Hosono. In numerical experiments the present method gives us an extremely accurate solution.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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