Kirchhoff scattering from underwater targets modeled as an assembly of triangular facets.

Abstract

Scattering from underwater targets is a challenging problem, mainly because many of the techniques developed in scattering theory are for radar applications and, therefore, appropriate only in free space. Underwater scattering occurs in a waveguide, which in most cases requires a modification if not a reformulation of the methods developed for scattering from targets in free space. The most accurate solution of scattering from a target in a waveguide can be obtained by solving the wave equation in an environment that contains the waveguide and the target and simultaneously imposing boundary conditions on the boundaries of the waveguide and on the surface of the target. However, this technique is numerically intensive making it impractical in most cases of interest. As a means of offering a more practical solution, we show how to solve the scattering problem from a target in a waveguide by (1) modeling it as an assembly of triangular facets, (2) computing scattering from each facet analytically using the Kirchhoff approximation for each set of incident and scattered plane waves, and (3) combining the solutions coherently. We compare this solution with those obtained using more accurate methods such as the virtual source technique.