A direct boundary element method for acoustic radiation and scattering from mixed regular and thin bodies

In this paper, the direct boundary element method is applied to acoustic radiation and scattering from mixed regular and thin bodies. A typical application problem involves a regular body with thin fins either attached to or in the neighborhood of the body. It is shown that the mixed-body integral formulation requires interactions between the conventional Helmholtz integral equation and the hypersingular thin-body integral equation. If at least one regular body is involved in a mixed-body environment, the direct integral formulation possesses the well-known nonuniqueness difficulty. This nonuniqueness difficulty is overcome by either the CHIEF method or the Burton and Miller method. Since both the thin-body integral equation and the Burton and Miller equation contain a hypersingular integral, a regularized form recently derived by Krishnasamy et al. [ASME J. Appl. Mech. 57, 404-414 (1990)] is adopted in this paper. Numerical results show excellent agreement with a multidomain boundary element solution and a point-source solution.