Canonical Seafloor Models and the Finite Difference Method for Low-Angle AcousticBackscatter. (Reannouncement with New Availability Information)

摘要

In order to study the physics of low-angle acoustic backscattering from theseafloor, we present a methodology based on the finite difference method for solving the two-way elastic wave equation. The method has many advantages including the ability to handle scattering (1) from surface and volume heterogeneities simultaneously, (2) from media with shear as well as compressional properties, (3) from heterogeneities with scale lengths on the order of the acoustic wavelengths, and (4) with a two-way formulation including multiple interactions between scatterers. The major problem in applying the finite difference method is to obtain low grazing angle incidence with reasonable grid sizes and without contamination from high angle energy. We discuss two approaches to this problem. In the first, we use the traditional point source in the water column but we attenuate energy in the undesired directions using the 'telegraph equation' around the source. In the second approach, we introduce a pulse-beam at the desired angle directly into the 'numerical scattering chamber.'