摘要:

AbstractNon‐linear responses of dam–reservoir systems are not well understood, because of the lack of an exact time‐domain solution for the far field (extending to infinity) of the fluid. This paper presents a procedure for efficient time‐domain analyses. It is based on a semi‐analytical solution and is suitable for the determination of the interactive behaviour of dam–reservoir systems.In this formulation, the fluid domain is divided into a near (to the dam) field, which is finite, and a far field extending to infinity. Arbitrary shapes of the upstream face of the dam, and of the bottom of the reservoir floor in the near field, are presumed. Furthermore, the far field is assumed to have a constant depth. The irregular near field is modelled by using the finite element method. A time‐domain semi‐analytical solution is obtained for the far field. For a vertical dam subjected to earthquake and ramp loadings, numerical solutions obtained compared well with the piecewise exact form of the anal

ISSN:0029-5981    

DOI:10.1002/nme.1620290502

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThis paper presents the development of an efficient and numerically stable algorithm for accurately computing the eigensolutions of the quadratic real symmetric eigenproblem arising in the finite dynamic element (FDE) formulation. Closely related to the subspace forward iteration method, the proposed scheme is well suited to extracting the lowest natural frequencies and associated mode shapes of large practical eigenproblems, takes full advantage of the banded configuration of the stiffness, inertia and dynamic correction matrices involved in the eigenproblem and ensures a monotonic convergence from above to the required eigenpairs. A shifting technique for convergence acceleration and an eigenpair verification scheme are also presented. Numerical examples are shown demonstrating the excellent performance of the solution procedure.

ISSN:0029-5981    

DOI:10.1002/nme.1620290503

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe coupled thermoviscoelastic response of a solid–fluid system is computed by a finite element formulation which involves only temperature and displacement fields. The Laplace transform with respect to time is applied to the coupled equations. This results in a global matrix in the transform domain that is symmetric and banded and the time response is obtained by numerical inversion of the transformed solution. Also, this formulation permits the use of fractional derivatives to model viscoelastic material behaviou

ISSN:0029-5981    

DOI:10.1002/nme.1620290504

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractA new fixed grid finite element technique for modelling phase‐change effects in steady‐state conduction–advection problems is described. The method is appropriate for materials that transform at a fixed critical temperature and is based on the assumption that the enthalpy experiences a jump discontinuity at this temperature, yielding a singular specific heat. This singularity is described using a Dirac delta function and the appropriate finite element matrix equations are developed for isoparametric elements. A simple first order upwinding scheme is used to avoid numerical oscillations in advection dominated problems. The utility of the method is illustrated through the solution of a one‐dimensional test problem using eight‐node hexahedral isoparametric finite elements. The technique may be applied to a wide range of finite element types and offers a number of advantages over other schemes for modelling phase‐cha

ISSN:0029-5981    

DOI:10.1002/nme.1620290505

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe free vibration of solids of revolution had never been solved by the Boundary Element Method (BEM) until a previous paper10by the authors, in which the BEM was combined with the method of particular integrals to solve axisymmetric free vibration problems. In this paper the previously developed analysis is extended to study the non‐axisymmetric free vibration of axisymmetric solids. The developed analysis has been implemented in a general purpose BEM system. Free vibrations of solid and hollow cylinders, a hyperbolic cooling tower and a gas turbine shell are used as examples, and their results are compared with those given by other methods. Except for low modes of very thin shells, good agreement can be see

ISSN:0029-5981    

DOI:10.1002/nme.1620290506

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractAn improved formulation for solving 2D transient scalar wave propagation problems by the Boundary Element Method (BEM) is presented. The kernels presented are simpler and better behaved than those that have appeared in the published literature. An appropriate set of temporal shape functions for linear variation is used. For spatial variations isoparametric quadratic elements are used. All of these represent significant improvements over the present level of sophistication in the analysis of 2D transient scalar problems. The algorithm is implemented in a general purpose boundary element code known as GPBEST.

ISSN:0029-5981    

DOI:10.1002/nme.1620290507

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractAn integral solution method based on the concept of the direct boundary element technique has been applied to develop a solution procedure for problems of diffusion with a non‐linear reaction in one dimension. The non‐linearity is handled by a process of quasi‐linearization over subintervals or elements in the main domain of integration. The weighting functions are defined for each subinterval such that the discretization is exact for the corresponding linear problem. This leads to a new powerful and simple method for the solution of this class of problems. A banded global matrix is obtained with both the concentration and its gradient as the unknown variables, and the problem is solved in an iterative manner. Illustrative results are presented for a test problem of diffusion with a second order reaction in an infinite slab, an infinite cylinder and spherical geometries. The accuracy of the method for situations with a sharp concentration gradient is demonstrated. The technique can also be used to numerically compute the solution in the boundary layer for fast reac

ISSN:0029-5981    

DOI:10.1002/nme.1620290508

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractIn this paper the finite element method (FEM) is used to analyse general, multiconductor transmission‐line systems of arbitrary cross‐section. The per‐unit‐length matrices of capacitance, inductance, conductance and resistance, which characterize a multiconductor transmission line, are obtained from the FEM analysis. Numerical results are presented and compared both with experimental results and other availab

ISSN:0029-5981    

DOI:10.1002/nme.1620290509

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractA new method of modelling the radiation effect in a time‐domain finite element analysis of semi‐infinite solids is proposed. The domain to be analysed is divided into a finite, interior region and a semi‐infinite, exterior region. The standard finite elements are used to model the interior region. An infinite element is used to model the semi‐infinite region. The main feature of the proposed method is the selection of semi‐infinite shape functions to develop the infinite element. A procedure is proposed whereby the necessary shape functions are derived directly from frequency‐domain analytical mode shapes. The interior and exterior regions are coupled by enforcing displacement continuity at the interface. The validity of the method is demonstrated in this paper by analysing a two‐dimensional, linear (damped), anti‐plane, shear‐wave (plane Love‐wave) propagation problem. The results obtained by the proposed method are compared with those obtained by direct finite element analysis with a fixed boundary placed sufficiently far from the location of loading to avo

ISSN:0029-5981    

DOI:10.1002/nme.1620290510

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractIn this study procedures for overcoming limit and bifurcation points in large‐scale structural analysis problems are described and evaluated. The methods are based on Newton's method for the outer iterations, while for the linearized problem in each iteration the preconditioned truncated Lanczos method is employed. Special care is placed upon line search routines for accelerating the convergence properties and enhancing the stability of the outer method. The proposed methodology retains all characteristics of an iterative method by avoiding the factorization of the current stiffness matrix. The necessary eigenvalue information is retained in the tridiagonal matrix of the Lanczos approac

ISSN:0029-5981    

DOI:10.1002/nme.1620290511

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY