ISSN:0029-5981    

DOI:10.1002/nme.1620380902

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe long‐term dynamic response of non‐linear geometrically exact rods under‐going finite extension, shear and bending, accompanied by large overall motions, is addressed in detail. The central objective is the design of unconditionally stable time‐stepping algorithms which exactly preserve fundamental constants of the motion such as the total linear momentum, the total angular momentum and, for the Hamiltonian case, the total energy. This objective is accomplished in two steps. First, a class of algorithms is introduced which conserves linear and angular momentum. This result holds independently of the definition of the algorithmic stress resultants. Second, an algorithmic counterpart of the elastic constitutive equations is developed such that the law of conservation of total energy is exactly preserved. Conventional schemes exhibiting no numerical dissipation, symplectic algorithms in particular, are shown to lead to unstable solutions when the high frequencies are not resolved. Compared to conventional schemes there is little, if any, additional computational cost involved in the proposed class of energy–momentum methods. The excellent performance of the new algorithm in comparison to other standard schemes is demonstrated in several numerical si

ISSN:0029-5981    

DOI:10.1002/nme.1620380903

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThis paper examines a new Galerkin method with scaled bubble functions which replicates the exact artificial diffusion methods in the case of 1‐D scalar advection–diffusion and that leads to non‐oscillatory solutions as the streamline upwinding algorithms for 2‐D scalar advection–diffusion and incompressible Navier–Stokes. This method retains the satisfaction of the Babuska–Brezzi condition and, thus, leads to optimal performance in the incompressible limit. This method, when, combined with the recently proposed linear unconditionally stable algorithms of Simo and Armero (1993), yields a method for solution of the incompressible Navier–Stokes equations ideal for either diffusive or advection‐dominated flows. Examples from scalar advection–diffusion and the solution of the incompressible Navier–Stokes eq

ISSN:0029-5981    

DOI:10.1002/nme.1620380904

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractIn this paper an out‐of‐core solver is developed for a three‐dimensional elastostatic boundary element program. This program includes multi‐regions which enables a large model to be divided into a number of homogeneous sub‐models, each with their own material properties. The system matrix produced by multi‐regions is sparse, blocked and unsymmetric in character and so reduces disc space and solution time. The solver presented in this paper utilizes efficiently the structure of this matrix by holding only non‐zero parts of this matrix in a sequential, unformatted direct access file, reading in as much of the file as possible into the working space, performing Gauss elimination, then writing part of the matrix back to file. The maximum utilization of working space is particularly important on vector machines as vector activity is maximized whilst record read/write is minimized. The effect of multi‐regions on CPU is demonstrated on both the CONVEX an

ISSN:0029-5981    

DOI:10.1002/nme.1620380905

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractA two‐dimensionalp‐type finite element scheme for distributed parallel computation of viscous flows is developed. The approach is based on an element‐by‐element implementation of the Biconjugate Gradient Stabilized 2 iterative method coupled with a recently developed class of block preconditioners. Critical to the overall parallel performance is the parallel solution of the imbedded bilinear preconditioner. Performance results are presented for the 2‐D driven cavity incompressible viscous flow problem solved using incremental continuation in the Reynolds number on the Intel Touchstone Delta. These results are used to validate a run‐time model. The run‐time model is then used to examine the scaling properties of the method over a

ISSN:0029-5981    

DOI:10.1002/nme.1620380906

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThis paper presents a methodology for the solution of an inverse solidification design problem in the presence of natural convection. In particular, the boundary heat fluxq0in the fixed mold wall, δΩ0, is calculated such that a desired freezing front velocity and shape are obtained. As the front velocity together with the flux historyqmson the solid side of the freezing front play a determinant role in the obtained cast structure, the potential applications of the proposed methods to the control of casting processes are enormous.The proposed technique consists of first solving a direct natural convection problem of the liquid phase in ana prioriknown shrinking cavity, ΩL(t), before solving an ill‐posed inverse design conduction problem in the solid phase in ana prioriknown growing region, ΩS(t). The direct convection problem is used to evaluate the fluxqmlin the liquid side of the freezing front. A front tracking deforming finite element technique is employed. The fluxqmlcan be used together with the Stefan condition to provide the freezing interface fluxqmsin the solid side of the front. As such, two boundary conditions (fluxqmsand freezing temperature θm) are especified along the (known) freezing interface δΩI(t). The developed design technique uses the adjoint method to calculate inL2the derivative of the cost functional, ∥θm– θ(x,t;q0)∥ L 22, that expresses the square error between the calculated temperature θ(x,t;q0) in the solid phase along δΩI(t) and the given melting temperature. The minimization of this cost functional is performed by the conjugate gradient method via the solutions of the direct, sensitivity and adjoint problems. A front tracking finite element technique is employed in this inverse analysis. Finally, an example is presented for the solidification of a superheated incompressible liquid aluminium, where the effects of natural convection in the moving interface shape are controlled with a proper adjustment of the cool

ISSN:0029-5981    

DOI:10.1002/nme.1620380907

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThis study is concerned with the development and implementation of a novel finite element which is capable of treating the problem of interacting circular inhomogeneities in heterogeneous solids. The general form of the element, which is constructed from a cell containing a single circular inhomogeneity in a surrounding matrix, is derived explicitly using the complex potentials of Muskhelishvili and the Laurent series expansion method. The strength of the proposed eight‐noded plane element is demonstrated by its ability to treat arbitrarily and periodically located multiple inhomogeneities under general loading conditions using a limited number of elements. Assessment of the accuracy and efficiency of the devised element is obtained by comparing its performance against existing analytical and traditional finite element attempts. The current element enables the determination of the local and effective elastic properties of composite materials with relative eas

ISSN:0029-5981    

DOI:10.1002/nme.1620380908

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

ISSN:0029-5981    

DOI:10.1002/nme.1620380909

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

ISSN:0029-5981    

DOI:10.1002/nme.1620380910

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

ISSN:0029-5981    

DOI:10.1002/nme.1620380901

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY