Summary
The finite element method with non-uniform mesh sizes is employed to approximately solve Helmholtz type equations in unbounded domains. The given problem on an unbounded domain is replaced by an approximate problem on a bounded domain with the radiation condition replaced by an approximate radiation boundary condition on the artificial boundary. This approximate problem is then solved using the finite element method with the mesh graded systematically in such a way that the element mesh sizes are increased as the distance from the origin increases. This results in a great reduction in the number of equations to be solved. It is proved that optimal error estimates hold inL 2,H 1 andL ∞, provided that certain relationships hold between the frequency, mesh size and outer radius.
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Goldstein, C.I. The finite element method with non-uniform mesh sizes applied to the exterior Helmholtz problem. Numer. Math. 38, 61–82 (1982). https://doi.org/10.1007/BF01395809
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DOI: https://doi.org/10.1007/BF01395809