### ASA 125th Meeting Ottawa 1993 May

## 2aUW13. Scattering from a rigid target in shallow water.

**Angie Sarkissian
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*Naval Res. Lab., Washington, DC 20375-5350
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An algorithm is developed to compute the field scattered from a rigid
target placed in shallow water. The method of superposition is applied where
the scattered field is approximated to be equivalent to the field produced by a
large number of point sources placed on a surface inside the target. The source
strengths are determined by minimizing the least-squares error of the normal
velocity on the surface of the target. This algorithm is applicable even when
the source or the receiver is close to the target as well as in the case where
the target is close to the surface. Scattering computations are made for a
cylinder with hemispherical endcaps in an isovelocity fluid with soft boundary
conditions on top and rigid boundary conditions on the bottom. They are
compared to the scattered field computed by using an algorithm discussed by
Ingenito [F. Ingenito, J. Acoust. Soc. Am. 82, 2051--2059 (1987)] for the case
when both the source and the receiver are distant from the target and when the
target is distant from the surface. Results from both methods agree in the
range of applicability of Ingenito's method.