摘要:

AbstractTwo kinds of techniques for solving a shape determination problem are proposed. The determination of the interface boundary between two domains governed by Poisson and Laplace equations under the compatible and constraint condition is considered. Influence coefficient and inverse variational approaches are examined by using the iterative finite element procedure. A two‐dimensional model of a junction‐type field effect transistor is a test example. The determination of its interface boundary and the prediction of the potential distribution and static characteristic are demonstra

ISSN:0029-5981    

DOI:10.1002/nme.1620190302

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractA finite strip method is presented for the geometrically nonlinear analysis of prismatic structures under arbitrary loading. The method employs an iterative finite element approach but replaces numerical integration by an explicit formulation. A computer program has been developed and is described in the paper; a numerical example is given.

ISSN:0029-5981    

DOI:10.1002/nme.1620190303

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractAn analysis of the stability and oscillation properties of upwind finite element methods for convection‐diffusion is given and used to develop a variable upwinding formulation. This formulation is particularly well suited to problems with nonconstant coefficients, nonlinearity or non‐uniform meshes. We present the theoretical analysis and numerical studies for a standard steady‐state and transient model one‐dimensional convection‐diffusion problem. The variable upwind strategy can also be used to significant advantage in conjunction with adaptive mesh refinement. Numerical results for the steady‐state case in which convection dominates and the mesh is adaptively refined into a boundary layer confirm the efficacy of

ISSN:0029-5981    

DOI:10.1002/nme.1620190304

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractThis paper contains numerical considerations on, and the results of the problem of a fluid filtering through a porous, isotropic, homogeneous, three‐dimensional dam with variable cross‐section. The numerical solution is obtained by the finite element method using cylindrical elements thatexactly matchthe curved part of the boundary.Furthermore, a lower and an upper numerical enclosure of the free boundary are considered, together with a description of the procedure of calculations performed by an IBM 370/158 compu

ISSN:0029-5981    

DOI:10.1002/nme.1620190305

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractPipe networks are computed in an analogous mannner to frameworks in structural mechanics loaded only by moments. The mesh method (force method) is applied. Due to the boundary layer effects in special pipe members, the flow problem is in general nonlinear. Therefore, the Newton‐Raphson iteration procedure is used to solve the nonlinear system of equations. Using the computed flow rates in the TREE structure (determined by graph theory) as initial values, the iteration procedure converges rapidly to a user specified tolerance value. The loss coefficients of pressure for different pipe members (TUBE, VALVE, BOW, TEE, PUMP, KNEE, ±CONTR, ±DIFSR) need only be given in diagrams. These diagrams are used in digitalized form. In the back‐substitution phase with known flow rates in all members, the pressure at the joints is computed.The main advantages of the analysis as outlined are that no initial values for the member flow rates need be known, the iteration procedure converges rapidly, and within each iteration step only small systems of linear equations need to be solved. Due to the fact that the loss coefficients of pressure need only be given in diagrams, arbitrary nonlinear networks can be analysed by the unchanged program system. A flow rate assumption may be specified in the input for a member of a mesh.The pressures at the joints are defined as unknowns (displacement method) in References 7, 8 and 10. The flow rates in the members are defined as unknowns (force method) in Reference 9. The nonlinear system of equations is always solved by the Newton‐Raphson procedure. In Reference 10 a strategy is presented to take into account different pipe members, but in a different way from that outlined in this paper. The members BOW, TEE, KNEE, CONTR, DIFSR are not examined in Refer

ISSN:0029-5981    

DOI:10.1002/nme.1620190306

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractA new, improved infinite element based on mapping is proposed for modelling unbounded domain problems. Mapping has previously been used in such problems, not only for the entire domain, but also for the infinite element itself. The novelty of the present approach is the simplicity of the mapping, and the retention of standard integration abscissae and weights. The implementation of these elements is very straightforward, and they are ideally suited for the analysis of infinite domain static problems in two and three dimensions.

ISSN:0029-5981    

DOI:10.1002/nme.1620190307

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractA stabilization procedure is developed for controlling the kinematic modes of the four‐node, bilinear quadrilateral element when single‐point quadrature is used. These kinematic modes manifest themselves by spatial oscillations or singularity of the total stiffness. In this stabilization procedure, additional generalized strains are defined which are activated by the kinematic modes; these generalized modes are furthermore not activated by rigid body motions regardless of the shape of the quadrilateral. By using a scaling law developed in an earlier paper, the stabilization parameters are defined so they do not adversely affect the element's performance. Several problems which are subject to kinematic modes are presented to illustrate the performance of this stabilization procedure for linear probl

ISSN:0029-5981    

DOI:10.1002/nme.1620190308

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractA new technique for the solution of singular integral equations is proposed, where the unknown function may have a particular singular behaviour, different from the one defined by the dominant part of the singular integral equation. In this case the integral equation may be discretized by two different quadratures defined in such a way that the collocation points of the one correspond to the integration points of the other. In this manner the system is reduced to an×nsystem of discrete equations and the method preserves, for the same number of equations, the same polynomial accuracy. The main advantage of the method is that it can proceed without using special collocation points. This new technique was tested in a series of typical examples and yielded results which are in good agreement with already existing solutions

ISSN:0029-5981    

DOI:10.1002/nme.1620190309

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractA uniform linear beam in a uniform linear ambient medium is studied. The beam performs stationary harmonic damped nonsynchronous space vibration in simultaneous tension, torsion, bending and shear in the presence of a large static axial load. Hysteretic and viscous dampings of the beam material and ambient medium are considered. Generalized complex Koloušek functions are derived. A 12 × 12 complex symmetric stiffness matrix is established for a supported beam member excited at its ends by prescribed harmonic translations and rotations which have the same frequency but may be out of phase. This matrix allows for an exact analysis of nonproportionally damped built‐up beam structures, thus avoiding assumed mode shapes and lumped or consistent masses. A general notation is suggested. Numerical examples are given, including applications of the computer program SFVIBAT

ISSN:0029-5981    

DOI:10.1002/nme.1620190310

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractIn this paper we extend predictor‐corrector methods, commonly used for the numerical solution of ordinary differential equations (o.d.e.s), to parabolic partial differential equations (p.d.e.s), typically of the formut=auxx+ ƒ(u,ux,x,t).We describe linear multistep methods for p.d.e.s, the nonlinear algebraic equations arising from implicit formulae being solved using a corrector analogous to those used for o.d.e.s. A sufficient condition for convergence of the iteration is then derived and is found, in most cases, to be far less restrictive than that obtained from the usual method of lines approach. Numerical results are presented to investigate the necessity of this condition. They also indicate that we can accelerate convergence by reducing the time increment. This allows us to achieve convergence within a prescribed number of iterations and so to constructPCmmethods corresponding toP(EC)mmethods for o.d.e.s. Numerical results are also given to test the absolute stability of the Crank‐Nicolson corrector for various predictorsP, and iteratio

ISSN:0029-5981    

DOI:10.1002/nme.1620190311

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY