摘要:

AbstractThe dual reciprocity boundary element method, first proposed by Nardini and Brebbia (1982, 1985), is a powerful technique for solving elliptic partial differential equations. Adopting this approach, a singular volume integral, which needs to be evaluated with a traditional boundary element method, can be converted into a boundary integral. However, when the governing equation is of a certain type, this conversion fails due to the singularities being introduced inside the physical domain and on the boundary arising by differentiating distance functions. We avoid these artificially created singularities by constructing a transformation which leads to improved numerical results.

ISSN:1069-8299    

DOI:10.1002/cnm.1640100502

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe paper demonstrates an approach to generate three‐dimensional boundary‐fitted computational meshes efficiently. One basic idea underlying the present study is that often similar geometries have to be meshed, and therefore an efficient mesh‐adaption method, which allows adaptation of the topological mesh to the specific geometry, would be more efficient than generating all new meshes. On the other hand the mesh generation for Cartesian topologies has been shown to be a very simple task. It can be executed by connecting and removing brick elements to a basic cube. In connection with a so‐called ‘Macro Command Language’, a high degree of automation can be reached when adapting topologically defined meshes to a surface. Furthermore, a high mesh quality has proved to be the key to good simulation results. During the mesh generation it is important to provide the possibility of modifiying the mesh quality and also the mesh density at any time of the meshing process. Using this generation method the meshing time is reduced—e.g. a computational mesh for a two‐valve cylinder head can be generated wit

ISSN:1069-8299    

DOI:10.1002/cnm.1640100503

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractA numerical problem which features prominently in the implementation of the boundary‐element method (BEM) for the solution of heat‐conduction problems arises from double‐valued heat fluxes at boundary corners. This problem is readily dealt with by explicitly treating nodal heat fluxes as double‐valued prior to assembly of the nodal equations. This formulation is very flexible as it also permits imposing discontinuous thermal conditions at any boundary node. However, at corner nodes where temperature only is prescribed, the scheme leads to two unknowns, while only one nodal BEM equation is available there. An additional equation which closely follows the previous work of Walker and Fenner is derived for these nodes, and this provides sufficient information to resolve the upstream and downstream values of the heat flux at the temperature node. The additional equation is general, is free of heuristic constraints, and is applicable through the wide range of acute, shallow, obtuse and re‐entrant angles encountered in practice. Numerical examples are used to compare the present method with the Walker and Fenner approach and with analytical solutions. Results indicate both improved accuracy and generality, thus validating the prese

ISSN:1069-8299    

DOI:10.1002/cnm.1640100504

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractIn this paper we present numerical experiments made to investigate the behaviour of the Newmark time‐stepping scheme applied to non‐linear dynamic systems. Our attention is focused on the instability and chaos in the Newmark scheme when it is applied to the equation ü +P(u)= 0, representing a non‐linear elastic spring. Some unusual modes of behaviour, which are of substantial interest, have been observed. In the first case, a stable but chaotic solution is found. In the second case, while a stable solution is obtained with a certain time step, an unstable solution is found bydecreasingthe time step. In the third case, instability is triggered by neglecting the initial acceleration. A simple modification of the Newmark scheme is proposed which keeps the energy constant for the equation ü +P(u)= 0 and thereby guarantees unconditional stability. Numerical examples in support of such an energy‐conserving scheme are

ISSN:1069-8299    

DOI:10.1002/cnm.1640100505

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractAn adaptive refinement/derefinement algorithm of nested meshes is presented. Some definitions are introduced. The main properties of the derefinement algorithm are remarked upon and its efficiency is shown through two numerical examples: a time‐dependent convection‐diffusion problems with dominant convection and a quasistationary prob

ISSN:1069-8299    

DOI:10.1002/cnm.1640100506

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractFracture in heterogeous solids can be simulated with finite elements. We compare simulations of mechanical breakdown using meshes based on two types of geometrical elements: quadrilaterals and hexagons. The different co‐ordination of the meshes leads to important differences in the load‐carrying geometry close to failure. Hexagonal elements give a better representation of failure in brittle solids, whereas quadrilateral elements have a resemblance to fibrous sol

ISSN:1069-8299    

DOI:10.1002/cnm.1640100507

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractA note on the effects of a weak discontinuity in the forcing functiong(x)of a singular, integral equation of the first kind and the resulting strong discontinuity that can appear in the solutionf(x) is presented.

ISSN:1069-8299    

DOI:10.1002/cnm.1640100508

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

ISSN:1069-8299    

DOI:10.1002/cnm.1640100509

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

ISSN:1069-8299    

DOI:10.1002/cnm.1640100501

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY