ASA 127th Meeting M.I.T. 1994 June 6-10

4aSA5. Exact analysis of the acoustic scattering by an arbitrarily insonified spherical body near a flat boundary.

H. Huang

G. Gaunaurd

Naval Surface Warfare Ctr., Dahlgren Div., White Oak Detachment, Silver Spring, MD 20903-5640

The acoustic scattering by spherical bodies (hard, soft, or elastic) near flat boundaries (hard or soft) insonified by plane waves at arbitrary incident angles is analyzed exactly in the low and intermediate frequency ranges. To satisfy the boundary conditions at the flat boundary as well as on the surface of the sphere, the mathematical problem is formulated using the image technique. The scattering wave fields are expanded in terms of the classical modal series of spherical wave functions utilizing the translational addition theorem. Quite similar to the problem of multiple scattering by spheres, numerical computation of the scattered wave pressure involves the solution of an ill-conditioned complex matrix system the size of which depends on how many terms of the modal series are required for convergence. This in turn depends on the value of the frequency, the proximity of the spherical body relative to the flat boundary and the incident angle. The ill-conditioned matrix equation can be solved using the Gauss--Seidel iteration method and back scattered echoes from the spherical bodies are extensively calculated. [Work supported by the NSWC Independent Research Program.]