ASA 126th Meeting Denver 1993 October 4-8

5pUW6. High-frequency forward scattering from Gaussian spectrum, pressure release, corrugated surfaces: Experiment and comparison with catastrophe theory.

J. S. Stroud P. L. Marston

Phys. Dept., Washington State Univ., Pullman, WA 99164-2814

K. L. Williams

Univ. of Washington, Seattle, WA

A single realization of a Gaussian spectrum surface, rms roughness 1.5 cm, correlation length 10 cm was manufactured out of styrofoam. This surface provided a pressure release, corrugated surface for an underwater, forward scattering investigation. Omni-directional source and receiver were used in the frequency range of 100 to 300 kHz. Short pulses were used to allow isolation of individual contributions to the scattered field. These individual contributions were then classified using catastrophe theory [M. V. Berry, ``Waves and Thom's Theorem,'' Advan. Phys. 25, 1--26 (1976); P. L. Marston, Physical Acoustics (Academic, New York, 1992), Vol. 21, pp. 1--234]. Scans at a constant distance from the mean of the rough surface were used to determine the peak forward scattered pressure. Composites of these types of scans are shown and discussed using catastrophe theory. The catastrophe theory simulation is shown to be a valid approximation to the wavefield for a wide range of frequencies. [Work supported by Office of Naval Research.]