摘要:

AbstractThe paper outlines the formulation of a novel algorithm which can be used for the solution of both compressible and incompressible Navier‐Stokes or Euler equations. Full incompressibility can be dealt with if the algorithm is used in its semi‐explicit form and its structure permits arbitrary interpolation functions to be used avoiding the Babuška‐Brezzi restriction. In a fully explicit version it introduces a rational form of balancing dissipation avoiding the use of arbitrary parameters and forms fo

ISSN:0271-2091    

DOI:10.1002/fld.1650200812

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe algorithm introduced in Part I of this paper is applied in its explicit form to a variety of problems in order to demonstrate its wide range of applicability and excellent performance. Examples range from nearly incompressible, viscous, flows through transonic applications to high speed flows with shocks. In most examples linear triangular elements are used in the finite element approximation, but some use of quadratic approximation, again in triangles, indicates satisfactory performance even in the case of severe shocks.

ISSN:0271-2091    

DOI:10.1002/fld.1650200813

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThis paper presents a methodology for solving shape optimization problems in the context of fluid flow problems including adaptive remeshing. The method is based on the computation of the sensitivities of the geometrical design parameters, the mesh, the flow variables and the error estimator to project the refinement parameters from one design to the next. This sensitivity analysis is described for the incompressible potential equations and the Euler equations. The efficiency of the proposed method is checked by means of two 2D inverse problems.

ISSN:0271-2091    

DOI:10.1002/fld.1650200814

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractVertex‐based multidimensional upwind schemes for scalar advection are compared with shock‐capturing SUPG finite element methods based on linear triangular elements. Both methods share the same compact stencil and are formulated as cell‐wise residual distribution methods. The distribution for the finite element method is 1/3, supplemented with a Lax‐Wendrov‐type dissipation term, while the distribution for the upwind schemes is limited to the downstream nodes of the element. The multidimensional upwind schemes use positivity as the monotonicity criterion, while the finite element method includes a residual‐based non‐linear dissipation.For hyperbolic systems such as the compressible Euler equations the upwind method relies on a multidimensional wave model to decompose the residual into scalar contributions. From this observation a new SUPG formulation for systems is proposed in which the scalar SUPG method is applied to each of the decomposed residuals obtained from the wave model, thereby providing a better‐founded definition of the τ dissipation matrix and shock‐capturing term i

ISSN:0271-2091    

DOI:10.1002/fld.1650200815

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractImplicit iterative schemes based on linearized and non‐linear Newton methods are discussed, with resolution of a matrix subsystem or a matrix‐free method by preconditioned GMRES algorithms. The defaults of convergence due to the locality of Newton algorithms can be partially overcome by using stabilizing descent techniques, restarting and global strategies such as line search backtracking procedures, or by tuning the iterations once the approximate Jacobians are closer to the exact ones. Comparison with a more conventional relaxation method and their implementation on parallel architectures are discus

ISSN:0271-2091    

DOI:10.1002/fld.1650200816

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractA fully coupled numerical model to simulate the slow transient phenomena involving heat and mass transfer in deforming porous media is developed. It makes use of the modified effective stress concept together with the capillary pressure relationship. The heat transfer through conduction and convection as well as the latent heat transfer (evaporation and/or condensation) is taken into account.The governing equations in terms of displacements, temperature, capillary pressure and gas pressure are coupled non‐linear differential equatiosn and are solved by the finite element method.The model is validated with respect to a documented experiment on semisaturated soil behaviour. Two other examples involving subsidence due to pumping from a phreatic aquifer and thermoelastic consolidation of saturated and semisaturated media are also presente

ISSN:0271-2091    

DOI:10.1002/fld.1650200817

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractIn this paper we describe a space‐time finite element method, with elements aligned along the computed characteristics in space‐time, for the computation of incompressible free surface flows in three dimensi

ISSN:0271-2091    

DOI:10.1002/fld.1650200818

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractWe present a method to assess the stability of pairs of interpolation spaces for mixed formulations. The method is based on a straightforward calculation of the eigenvalues of the discrete matrices through Fourier decomposition in plane waves and is intended to give, via straightforward numerical computations, a sharper determination of stability than the well‐known ‘patch test’ of Zienkiewiczet al.Special attention is devoted to the study of stability and accuracy of equal‐order interpo

ISSN:0271-2091    

DOI:10.1002/fld.1650200819

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractEmployment of hybrid prismatic/tetrahedral grids is a relatively new approach for viscous flow computations with 3D complex geometries. The body surface is covered with triangles, which provides geometric flexibility, while the structure of the mesh in the direction normal to the surface provides thin prismatic elements suitable for the viscous region. The outermost layer of the prismatic grid is then used as the inner boundary surface for a tetrahedral grid which covers the rest of the computational domain. The hybrid grid is employed for performing Navier‐Stokes calculations in the prismatic region near the body and Euler calculations in the tetrahedral regions away from the body.The generation method of hybrid prismatic/tetrahedral grids marches a triangulated surface mesh away from the body to form a semi‐unstructured prismatic grid. Tetrahedra are then constructed which are linked directly to the nodes of the outermost prismatic layer. The hybrid grid is locally refined over both the prismatic and tetrahedral regions. Directional embedding of the prisms preserves the structure of the mesh in thenormal‐to‐surfacedi

ISSN:0271-2091    

DOI:10.1002/fld.1650200820

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe equations describing the mechanical behaviour of intervertebral disc tissue and other swelling porous media are three coupled partial differential equations in which geometric and physical non‐linearities occur. The boundary conditions are deformation‐dependent. To solve the equations for an arbitrary geometry and arbitrary boundary conditions, we use the finite element (FE) method. The differential equations are rewritten in an integral form by means of the weighted residual method. The domain of the integral is defined via a set of shape functions (i.e. finite elements). By applying the Gauss theorem and rewriting with respect to the reference state (total Lagrange), non‐linear equations are obtained. These are solved by means of the Newton‐Raphson technique. In order to get a finite set of equations, the weighted residual equations are discretized. The shape functions are chose as weighting functions (Galerkin method). This discretization results in a non‐symmetric stiffness matrix. A general description is given for the elements implemented into the commercial FE package DIANA (DIANA Analysis B.V., Delft, Netherlands). The numerical results of unconfined compression of a schematic intervertebral disc with varying proteoglycan concentration

ISSN:0271-2091    

DOI:10.1002/fld.1650200821

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY