Simulations of rough boundary effects on shallow water propagation

Abstract

Results of PE simulations will be described for propagation in a shallow water waveguide with a rough sea surface and a flat seafloor. Pressure fields are simulated in two space dimensions and have been obtained using a wide‐angle PE code developed by Rosenberg [A. D. Rosenberg, J. Acoust. Soc. Am. 105, 144–153 (1999)]. At a frequency near 3 kHz and with typical sea conditions, the behavior of the forward scattered field is found to depend dramatically on the incident grazing angle. A narrow incident beam at a 10° grazing angle is completely broken up, with energy scattered widely in angle. At a 1° angle, little energy is scattered out of the beam. Examples will also be shown for the more typical case of a relatively broad beam with a wide range of grazing angles at the surface. At low frequency, such as 100 Hz, it is useful to represent shallow water fields in terms of normal modes. Results of PE simulations using single mode initial fields and sinusoidal surfaces will be used to illustrate the effects of surface scattering on mode propagation and on mode couplings. [Work supported by ONR.]