ASA 124th Meeting New Orleans 1992 October

5aUW13. Numerical integral equation solution for scattering from a one-dimensional penetrable fluid interface and a buried rigid cylinder.

Daniel O. Ludwigsen

Dajun Tang

Dept. of Appl. Ocean Phys. and Eng., Woods Hole Oceanographic Inst., Woods Hole, MA 02543

Ocean bottom scattering problems involve contributions from both the roughness of the seafloor and inhomogeneities within the sediment or buried objects. Here, a numerical procedure has been developed to find an exact solution for scattering from an infinitely long rigid cylinder buried beneath a one-dimensional rough interface. In this model, the water--sediment interface is a penetrable fluid boundary with the conditions that pressure and vertical particle velocity are continuous. The cylinder surface is rigid, i.e., the vertical particle velocity on the boundary is zero. A boundary integral approach is used: the pressure field and its normal derivative on the rough surface, and the pressure field on the cylinder surface, are determined, then used to find the far-field scattered field. This method was previously used for a pressure-release boundary condition [E. I. Thorsos, J. Acoust. Soc. Am. 83, 78--92 (1988)] and the penetrable boundary [E. I. Thorsos, J. Acoust. Soc. Am. 90, 2232(A) (1991)]. It is now developed for the combination of a penetrable boundary and a rigid cylinder to validate possible approximation methods. As a benefit of this formalism, the shape of the buried object may be readily varied to model elliptical and perhaps other cylinder cross sections.