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Computational Science, Engineering & Technology Series
ISSN 1759-3158 CSETS: 18
COMPUTATIONAL METHODS FOR ACOUSTICS PROBLEMS Edited by: F. Magoulès
Chapter 5
Boundary Conditions and Iterative Schemes for the Helmholtz Equation in Unbounded Regions E. Turkel
School of Mathematical Sciences, Tel Aviv University, Israel E. Turkel, "Boundary Conditions and Iterative Schemes for the Helmholtz Equation in Unbounded Regions", in F. Magoulès, (Editor), "Computational Methods for Acoustics Problems", Saxe-Coburg Publications, Stirlingshire, UK, Chapter 5, pp 127-158, 2008. doi:10.4203/csets.18.5
Keywords: Helmholtz equation, Krylov methods, preconditioning, absorbing boundary
conditions.
Abstract
We consider the numerical solution of the Helmholtz equation in unbounded regions.
Given an interior discretisation this requires the construction of an artificial surface to
bound the domain of interest and the specification of a boundary condition that limits
the reflections of waves back into the interior region. We discuss various options
for this absorbing boundary condition. The resultant complex valued system of
non-Hermitian equations needs to be solved. For high frequencies a direct solver is no
longer feasible. The iterative method is usually a Krylov space technique. To speed
the convergence a preconditioner is introduced. Various types of preconditioners are
described.
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