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A sinh tranformation for evaluating nearly singular boundary element integrals


Johnston, PR and Elliott, D, A sinh tranformation for evaluating nearly singular boundary element integrals, International Journal for Numerical Methods in Engineering, 62, (4) pp. 564-578. ISSN 0029-5981 (2005) [Refereed Article]

DOI: doi:10.1002/nme.1208


An implementation of the boundary element method requires the accurate evaluation of many integrals. When the source point is far from the boundary element under consideration, a straightforward application of Gaussian quadrature suffices to evaluate such integrals. When the source point is on the element, the integrand becomes singular and accurate evaluation can be obtained using the same Gaussian points transformed under a polynomial transformation which has zero Jacobian at the singular point. A class of integrals which lies between these two extremes is that of 'nearly singular' integrals. Here, the source point is close to, but not on, the element and the integrand remains finite at all points. However, instead of remaining flat, the integrand develops a sharp peak as the source point moves closer to the element, thus rendering accurate evaluation of the integral difficult. This paper presents a transformation, based on the sinh function, which automatically takes into account the position of the projection of the source point onto the element, which we call the 'nearly singular point', and the distance from the source point to the element. The transformation again clusters the points towards the nearly singular point, but does not have a zero Jacobian. Implementation of the transformation is straightforward and could easily be included in existing boundary element method software. It is shown that, for the two-dimensional boundary element method, several orders of magnitude improvement in relative error can be obtained using this transformation compared to a conventional implementation of Gaussian quadrature. Asymptotic estimates for the truncation errors are also quoted. Copyright © 2004 John Wiley & Sons, Ltd.

Item Details

Item Type:Refereed Article
Research Division:Mathematical Sciences
Research Group:Numerical and computational mathematics
Research Field:Numerical analysis
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the mathematical sciences
UTAS Author:Elliott, D (Professor David Elliott)
ID Code:36544
Year Published:2005
Web of Science® Times Cited:83
Deposited By:Mathematics
Deposited On:2005-08-01
Last Modified:2012-03-01

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