ASA 124th Meeting New Orleans 1992 October

5aUW6. Application of the finite-element method to low-frequency mode conversion and reflection.

Joseph E. Murphy

Gongqin Li

Dept. of Phys., Univ. of New Orleans, New Orleans, LA 70148

Stanley A. Chin-Bing

Naval Res. Lab. Det., Stennis Space Center, MS 39529

A finite-element model is used to compute acoustic pressure in an inhomogeneous region, and coupled to mode expansions on the left and right boundaries of that region. By allowing the incident field to consist of a single mode, one can determine a mode scattering matrix, i.e., the amplitudes for backscattered modes and amplitudes for modes transmitted through the far boundary. The modal expansions used on the two boundaries need not be the same. Examples with rapid bathemetry changes and strong range-dependent changes in sound speed and density will be shown. [Work supported by ONR and the ONR Acoustic Reverberation SRP.]