Browsing by Author "Dors, Cleberson"

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    Analysis of 3D time-dependent acoustic problems via a generic BE substructuring algorithm based on iterative solvers.
    (2003) Araújo, Francisco Célio de; Alberto, Denival Rogério; Dors, Cleberson
    In this paper, a generic BE/BE coupling algorithm based on iterative solvers is applied to solve 3D time-dependent acoustic problems. As regards the treatment of the time-dependence, a direct time-marching scheme is considered. Several types of boundary elements and cells are available in the code for the spatial description of the involved variables. Concerning the BE/BE coupling technique, its chief idea is to completely avoid storing and manipulating the zero blocks appearing in the coupled system by the use of iterative solvers. The global system matrix is not explicitly assembled; instead the algebraic subsystems (associated with the substructures of the model) are manipulated as they were independent of each other. An insight into the coupling strategy and the used iterative solver (Jacobi-preconditioned bi-conjugate gradient method) is given. Analyses of sound barriers are carried out for verifying the performance of the respective computational code modules.
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    New developments on BE/BE multi-zone algorithms based on krylov solvers - applications to 3D frequency-dependent problems.
    (2004) Araújo, Francisco Célio de; Mansur, Webe João; Dors, Cleberson; Martins, Cláudio José
    In this paper, new developments concerning the use of BE/BE coupling algorithms for solving 3D time-harmonic problems are reported. The algorithms are derived by considering different iterative solvers. Their chief idea is to work with the global sparse matrix of the coupled system, however without considering the many zero blocks associated with the non-coupled nodes of different subregions. The use of iterative solvers makes it possible to store and manipulate only the block matrices with non-zero coefficients. Preconditioned iterative solvers based on the Lanczos, bi-conjugate gradient, and GMRES (generalized minimal residual) methods are used to derive the BE/BE coupling algorithms. A description of the formulation of these solvers, which are completely general and can be applied to any non-singular, non-hermitian systems of equations, is provided. The performance of the algorithms is verified by solving some foundation-soil interaction problems. Important parameters for estimating the efficiency of the algorithms as required CPU times, matrix sparsity, and accuracy of the obtained responses are presented in the results of the paper.
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    Paralelização de algoritmos MEC via subestruturação baseada em solvers iterativos - aplicação a problemas 3D escalares e vetoriais.
    (2002) Dors, Cleberson; Araújo, Francisco Célio de
    Neste trabalho, são apresentados novos desenvolvimentos de pesquisa relacionados com algoritmos de acoplamento BE/BE, utilizados na análise de problemas 3D estáticos e tempo-harmônicos. Os algoritmos são derivados considerando-se diferentes solvers iterativos, e a idéia principal dos mesmos é trabalhar com a matriz esparsa global do sistema acoplado, porém sem levar em conta qualquer dos grandes blocos de zeros associados com os nós desacoplados das diferentes sub-regiões. O uso de solvers iterativos torna possível armazenar e manipular somente blocos de coeficientes não nulos das matrizes, durante o processo de análise. Eficientes solvers pré-condicionados baseados nos métodos de Lanczos, Gradiente Bi-conjugado (BI-CG) e Resíduo Mínimo Generalizado (GMRES) são usados neste trabalho, para derivar os algoritmos de acoplamento BE/BE. Uma descrição da formulação destes solvers, que são completamente gerais e podem ser aplicados a qualquer sistema de equações não singular e não hermitiano, é apresentada.A performance dos algoritmos é verificada através da resolução de alguns problemas. São apresentados nos resultados do trabalho, parâmetros importantes para estivar a eficiência dos algoritmos, como tempos de CPU, esparsidade matricial e precisão das respostas obtidas.Implementa-se também um algoritmo paralelo, a partir da estratégia de acoplamento formulada, verificando-se sua performance através de parâmetros de eficiência convenientes.