### 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
**

**
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*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.]