ASA 127th Meeting M.I.T. 1994 June 6-10

5pUW6. Inclusion of rough surface scattering in a finite element parabolic equation propagation model.

Guy V. Norton

Naval Res. Lab., Stennis Space Center, MS 39529-5004

Jorge C. Novarini

Planning Systems, Inc., Slidell, LA 70458

Richard S. Keiffer

Naval Res. Lab., Stennis Space Center, MS 39529-5004

Propagation models in underwater acoustics usually incorporate surface scattering effects in an ad-hoc manner that in most cases requires making severe approximations. In particular, to include surface scattering in a marching algorithm for sound propagation in a coherent manner posses a difficult problem. Dozier [J. Acoust. Soc. Am. 75, 1415--1432 (1984)] introduced a novel and rigorous approach to include surface scattering in the framework of the split-step parabolic equation method. In this work the technique developed by Dozier is adapted and implemented in the realm of the finite element parabolic equation (FEPE) acoustic propagation model developed by Collins [J. Acoust. Soc. Am. 86, 1097 (1989)]. The technique is tested by applying it to scattering from a sinusoidal patch as well as from a rough surface patch defined by a Pierson--Moskowitz spectrum. These results are compared against highly accurate solutions to the surface scattering integral equation (method of moments). [Work supported by ONR.]