Plane-wave basis finite elements and boundary elements for three-dimensional wave scattering

• Published in: Philosophical transactions of the Royal Society of London. Series A: Mathematical, physical, and engineering sciences Vol. 362; no. 1816; pp. 561 - 577
• Main Authors: Perrey-Debain, E., Laghrouche, O., Bettess, P., Trevelyan, J.
• Format: Journal Article
• Language: English
• Published: England The Royal Society 15.03.2004; Royal Society, The
• Subjects: Amplitude; Approximation; Boundary conditions; Boundary Elements; Degrees of freedom; Differential equations; Engineering Sciences; Finite Elements; High frequencies; Plane Waves; Textual collocation; Vertices; Wave Scattering; Wavelengths
• ISSN: 1364-503X; 1471-2962
• DOI: 10.1098/rsta.2003.1335

Classical finite-element and boundary-element formulations for the Helmholtz equation are presented, and their limitations with respect to the number of variables needed to model a wavelength are explained. A new type of approximation for the potential is described in which the usual finite-element and boundary-element shape functions are modified by the inclusion of a set of plane waves, propagating in a range of directions evenly distributed on the unit sphere. Compared with standard piecewise polynomial approximation, the plane-wave basis is shown to give considerable reduction in computational complexity. In practical terms, it is concluded that the frequency for which accurate results can be obtained, using these new techniques, can be up to 60 times higher than that of the conventional finite-element method, and 10 to 15 times higher than that of the conventional boundary-element method.