Development of the direct boundary element method for thin bodies with general boundary conditions

A direct boundary element method (DBEM) is developed for thin bodies whose surfaces are rigid or compliant. The Helmholtz integral equation and its normal derivative integral equation are adopted simultaneously to calculate the pressure or the velocity potential on both sides of thin body, instead of the jump values across it, to account for the different surface conditions of each side. Unlike the usual assumption, the normal velocity is assumed to be discontinuous across the thin body. In this approach, only the neutral surface of the thin body has to be discretized. The method is validated by comparison with analytical and/or numerical results for acoustic scattering and radiation from the surface of a thin body under several conditions: when the surfaces are rigid while stationary or vibrating, and when part of the interior is lined with a sound absorbing material. (C) 1997 Academic Press Limited.