ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

2pUW6. Moderate frequency scattering from objects in an elastic bottom with rough interfaces.

Jaiyong Lee

Henrik Schmidt

Dept. of Ocean Eng., MIT, Cambridge, MA 02139

The diffuse reverberation from small scale bottom roughness severely affects the spatial coherence of the scattered field from near-bottom buried objects. To investigate this phenomenon theoretically, a numerical model is being developed for moderate frequency scattering from an elastic inclusion in a stratified, rough bottom. The model combines theories for object scattering and small-scale rough interface scattering. For the numerical implementation, a global approach is introduced, which combines three different methods into a consistent hybrid scheme. Boundary elements are used to compute the effects due to an elastic inclusion [P. Gerstoft and H. Schmidt, J. Acoust. Soc. Am. 89, 1629--1642 (1991)], wave-number integration provides numerical Green's function for the horizontally stratified medium, and finally the rough interface scattering is handled using a self-consistent perturbational method [W. A. Kuperman and H. Schmidt, J. Acoust. Soc. Am. 86, 1511--1522 (1989)]. Compared to earlier implementations, the efficiency of the boundary element component of the model has been significantly improved by introducing a new analytical integration approach to the computation of the influence matrices. The modeling approach will be described and its application to realistic sonar scenarios will be demonstrated. [Work supported by ONR.]