Efficient "black-box" Multigrid Solvers for Convection-dominated Problems PDF Download
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Author: Glyn Owen Rees
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Glyn Owen Rees
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Ignacio M. Llorente
Publisher:
ISBN:
Category : Boundary value problems
Languages : en
Pages : 36
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Book Description
Multigrid algorithms are known to be highly efficient in solving systems of elliptic equations. However, standard multi grid algorithms fail to achieve optimal grid-independent convergence rates in solving non-elliptic problems. In many practical cases, the non-elliptic part of a problem is represented by the convection operator. Downstream marching, when it is viable, is the simplest and most efficient way to solve this operator. However, in a parallel setting, the sequential nature of marching degrades the efficiency of the algorithm. The aim of this report is to present, evaluate and analyze an alternative highly parallel multi grid method for 3-D convection-dominated problems. This method employs semi coarsening, a four-color plane-implicit smoother, and discretization rules allowing the same cross-characteristic interactions on all the grids involved to be maintained. The resulting multigrid solver exhibits a fast grid-independent convergence rate for solving the convection-diffusion operator on cell-centered grids with stretching. The load imbalance below the critical level is the main source of inefficiency in its parallel implementation. A hybrid smoother that degrades the convergence properties of the method but improves its granularity has been found to be the best choice in a parallel setting. The numerical and parallel properties of the multi grid algorithm with the four-color and hybrid smoothers are studied on SGI Origin 2000 and Cray T3E systems.
Author: Stefan Turek
Publisher: Springer Science & Business Media
ISBN: 3642583938
Category : Mathematics
Languages : en
Pages : 369
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Book Description
A discussion of recent numerical and algorithmic tools for the solution of certain flow problems arising in CFD, which are governed by the incompressible Navier-Stokes equations. The book contains the latest results for the numerical solution of (complex) flow problems on modern computer platforms, with particular emphasis on the solution process of the resulting high dimensional discrete systems of equations which is often neglected in other works. Together with the accompanying CD ROM containing the complete FEATFLOW 1.1 software and parts of the "Virtual Album of Fluid Motion", readers are able to perform their own numerical simulations and will find numerous suggestions for improving their own computational simulations.
Author: Wolfgang Dahmen
Publisher:
ISBN:
Category :
Languages : en
Pages : 40
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Author: Victor Alan Bandy
Publisher:
ISBN:
Category : Differential equations, Partial
Languages : en
Pages : 688
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Author: Sabine Le Borne
Publisher:
ISBN: 9783933342560
Category :
Languages : en
Pages : 145
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 21
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Book Description
A two-level analysis method for certain separable problems is introduced. It motivates the definition of improved versions of Black Box Multigrid for diffusion problems with discontinuous coefficients and indefinite Helmholtz equations. For anisotropic problems, it helps in choosing suitable implementations for frequency decomposition multigrid methods. For highly indefinite problems, it provides a way to choose in advance a suitable mesh size for the coarsest grid used. Numerical experiments confirm the analysis and show the advantage of the present methods for several examples.
Author: Sergey I. Martynenko
Publisher: Walter de Gruyter GmbH & Co KG
ISBN: 3110539268
Category : Mathematics
Languages : en
Pages : 212
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Book Description
This book presents a detailed description of a robust pseudomultigrid algorithm for solving (initial-)boundary value problems on structured grids in a black-box manner. To overcome the problem of robustness, the presented Robust Multigrid Technique (RMT) is based on the application of the essential multigrid principle in a single grid algorithm. It results in an extremely simple, very robust and highly parallel solver with close-to-optimal algorithmic complexity and the least number of problem-dependent components. Topics covered include an introduction to the mathematical principles of multigrid methods, a detailed description of RMT, results of convergence analysis and complexity, possible expansion on unstructured grids, numerical experiments and a brief description of multigrid software, parallel RMT and estimations of speed-up and efficiency of the parallel multigrid algorithms, and finally applications of RMT for the numerical solution of the incompressible Navier Stokes equations. Potential readers are graduate students and researchers working in applied and numerical mathematics as well as multigrid practitioners and software programmers. Contents Introduction to multigrid Robust multigrid technique Parallel multigrid methods Applications of multigrid methods in computational fluid dynamics
Author: Manuel Prieto
Publisher:
ISBN:
Category : Multigrid methods (Numerical analysis)
Languages : en
Pages : 26
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Abstract: "This paper presents an efficient parallel multigrid solver for speeding up the computation of a 3-D model that treats the flow of a viscous fluid over a flat plate. The main interest of this simulation lies in exhibiting some basic difficulties that prevent optimal multigrid efficiencies from being achieved. As the computing platform, we have used Coral, a Beowulf-class system based on Intel Pentium processors and equipped with GigaNet cLAN and switched Fast Ethernet networks. Our study not only examines the scalability of the solver but also includes a performance evaluation of Coral where the investigated solver has been used to compare several of its design choices, namely, the interconnection network (GigaNet versus switched Fast-Ethernet) and the node configuration (dual nodes versus single nodes). As a reference, the performance results have been compared with those obtained with the NAS-MG benchmark."
Author: Jim E. Jones
Publisher:
ISBN:
Category : Anisotropy
Languages : en
Pages : 18
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Book Description
Abstract: "Efficient and robust multigrid solvers for anisotropic problems typically use either semi-coarsened grids or implicit smoothers -- line relaxation in 2D and plane relaxation in 3D. However, both of these may be difficult to implement in codes using multi-block structured grids where there may be no natural definition of a global 'line' or 'plane'. These multi-block structured grids are often used in fluid dynamic applications to capture complex geometries and/or to facilitate parallel processing. In this paper, we investigate the performance of multigrid algorithms using implicit smoothers within the blocks of a such a [sic] grid. By looking at a model problem, the 2-D anisotropic diffusion equation, we show that true multigrid efficiency is achieved only when the block sizes are proportional to the strength of the anisotropy. Further, the blocks must overlap and the size of the overlap must again be proportional to the strength of the anisotropy."
