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The performance of spheroidal infinite elements

The performance of spheroidal infinite elements
The performance of spheroidal infinite elements
A number of spheroidal and ellipsoidal infinite elements have been proposed for the solution of unbounded wave problems in the frequency domain, i.e solutions of the Helmholtz equation. These elements are widely believed to be more effective than conventional spherical infinite elements in cases where the radiating or scattering object is slender or flat and can therefore be closely enclosed by a spheroidal or an ellipsoidal surface. The validity of this statement is investigated in the current article. The radial order which is required for an accurate solution is shown to depend strongly not only upon the type of element that is used, but also on the aspect ratio of the bounding spheroid and the non-dimensional wave number. The nature of this dependence can partially be explained by comparing the non-oscillatory component of simple source solutions to the terms available in the trial solution of spheroidal elements. Numerical studies are also presented to demonstrate the rates at which convergence can be achieved, in practice, by unconjugated-(Burnett) and conjugated (Astley-Leis)-type elements. It will be shown that neither formulation is entirely satisfactory at high frequencies and high aspect ratios.
infinite elements, spheroidal co-ordinates, helmholtz equation, convergence
0029-5981
1379-1396
Astley, R.J.
cb7fed9f-a96a-4b58-8939-6db1010f9893
Coyette, J.-P.
bbc978d8-d8e9-4148-b758-76184399441e
Astley, R.J.
cb7fed9f-a96a-4b58-8939-6db1010f9893
Coyette, J.-P.
bbc978d8-d8e9-4148-b758-76184399441e

Astley, R.J. and Coyette, J.-P. (2001) The performance of spheroidal infinite elements. International Journal for Numerical Methods in Engineering, 52 (12), 1379-1396. (doi:10.1002/nme.260).

Record type: Article

Abstract

A number of spheroidal and ellipsoidal infinite elements have been proposed for the solution of unbounded wave problems in the frequency domain, i.e solutions of the Helmholtz equation. These elements are widely believed to be more effective than conventional spherical infinite elements in cases where the radiating or scattering object is slender or flat and can therefore be closely enclosed by a spheroidal or an ellipsoidal surface. The validity of this statement is investigated in the current article. The radial order which is required for an accurate solution is shown to depend strongly not only upon the type of element that is used, but also on the aspect ratio of the bounding spheroid and the non-dimensional wave number. The nature of this dependence can partially be explained by comparing the non-oscillatory component of simple source solutions to the terms available in the trial solution of spheroidal elements. Numerical studies are also presented to demonstrate the rates at which convergence can be achieved, in practice, by unconjugated-(Burnett) and conjugated (Astley-Leis)-type elements. It will be shown that neither formulation is entirely satisfactory at high frequencies and high aspect ratios.

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Published date: 2001
Keywords: infinite elements, spheroidal co-ordinates, helmholtz equation, convergence

Identifiers

Local EPrints ID: 10198
URI: http://eprints.soton.ac.uk/id/eprint/10198
ISSN: 0029-5981
PURE UUID: 3db2fcdc-fbfb-4182-a5f9-eede75f0e627

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Date deposited: 09 May 2005
Last modified: 15 Mar 2024 04:58

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Contributors

Author: R.J. Astley
Author: J.-P. Coyette

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