3-D acoustic scattering from 2-D rough surfaces using a parabolic equation model

Abstract

Rough surface scattering plays a crucial role in the statistics of acoustic propagation signals, especially at mid-frequencies and higher (e.g., acoustic communications systems). For many years, the effects of rough surface scattering were computed using simple models that were applied in two dimensions (2-D) only. A prescribed method of computing 2-D rough surface scattering directly in a parabolic equation model based on the Split-Step Fourier algorithm was introduced by Tappert and Nghiem-Phu in the mid-1980s. This method has been successfully implemented in various 2-D parabolic equation models, including the Monterey Miami Parabolic Equation model. However, some scientific research of more formal scattering predictions have suggested that out-of-plane, three dimensional (3-D) scattering may lead to significant disparities in the scattered field statistics. Introducing a hybrid implementation for the scattering effect in the field transformation equations using a tri-diagonal solution with the Pad approximant to obtain a system of equations for azimuthal corrections will support predictions of the effect of surface scattering on 3-D propagation, which is critical in evaluating the variability in underwater acoustic propagation. Results of the 3-D scattering calculations obtained are compared with the output of basic 2-D interface perturbations utilizing the standard 2-D approach.