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Abstract.We consider a non-overlapping domain decomposition method for diffusion-reaction problems which is known to converge strongly from previous work. We derive an a posteriori estimate which bounds the errors on the subdomains by the difference of traces of the subdomain solutions. If the domain decomposition method is discretized by finite elements we can adapt the techniques of the usual a...
Abstract.Iterative methods with variable preconditioners of additive type are proposed. The scaling factors of each summand in the additive preconditioners are optimized within each iteration step. It is proved that the presented methods converge at least as fast as the Richardsons iterative method with the corresponding additive preconditioner with optimal scaling factors. In the presented numerical...
Abstract.Nonconforming finite element discretisations require special care in the construction of the prolongation and restriction in the multigrid process. In this paper, a general scheme is proposed, which guarantees the approximation property. As an example, the technique is applied to the discretisation by non-matching grids (mortar elements).
Abstract The application of a non-overlapping domain decomposition method to the solution of a stabilized finite element method for elliptic boundary value problems is considered. We derive an a-posteriori error estimate which bounds the error on the subdomains by the interface error of the subdomain solutions. As a by-product, some foundation is given to the design of the interface transmission condition...
Abstract We consider multigrid methods for problems in linear elasticity which are robust with respect to the Poisson ratio. Therefore, we consider mixed approximations involving the displacement vector and the pressure, where the pressure is approximated by discontinuous functions. Then, the pressure can be eliminated by static condensation. The method is based on a saddle point smoother which was...
Abstract To solve the elliptic boundary value problems with singularities, the simplified hybrid combinations of the Ritz-Galerkin and finite element methods (RGM-FEM) are explored to lead to the global superconvergence rates on the entire solution domain, based on an a posteriori interpolation techniques of Lin and Yan [12] that only cost a little more computation. Let the solution domain S=S1S20...
Abstract In this paper smoothing properties are shown for a class of iterative methods for saddle point problems with smoothing rates of the order 1/m, where m is the number of smoothing steps. This generalizes recent results by Braess and Sarazin, who could prove this rates for methods where, in the context of the Stokes problem, the pressure correction equation is solved exactly, which is not needed...
Abstract We present a novel automatic grid generator for the finite element discretization of partial differential equations in 3D. The grids constructed by this grid generator are composed of a pure tensor product grid in the interior of the domain and an unstructured grid which is only contained in boundary cells. The unstructured component consists of tetrahedra, each of which satisfies a maximal...
AbstractOne of the most popular pairs of finite elements for solving mixed formulations of the Stokes and NavierStokes problem is the QkPk1disc element. Two possible versions of the discontinuous pressure space can be considered: one can either use an unmapped version of the Pk1disc space consisting of piecewise polynomial functions of degree at most k1 on each cell or define a mapped version where...
Abstract In this paper, we present a new approach to construct robust multilevel algorithms for elliptic differential equations. The multilevel algorithms consist of multiplicative subspace corrections in spaces spanned by problem dependent generalized prewavelets. These generalized prewavelets are constructed by a local orthogonalization of hierarchical basis functions with respect to a so-called...
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