Multisector Parabolic Equation Method for Scattering From Impenetrable Objects in Fluid Waveguides

Parabolic equation methods are a robust and efficient tool for modeling long-range acoustic propagation in range-dependent waveguides. A lesser known, but equally effective, application of parabolic equations is to the scattering problem. In this paper, we study the applicability and accuracy of the multisector parabolic equation approach to scattering from impenetrable objects - first developed approximately two decades ago for convex objects and recently extended to more complex scatterers - in waveguides in two and three dimensions. We benchmark the method in two dimensions in a range-dependent waveguide consisting of two different fluid media and find very good agreement with finite element methods for both forward scattering and backscattering, including the case where the scatterer is located at the interface between the media. Finally, we provide an example of scattering in a large three-dimensional waveguide, which would be extremely computationally intensive using alternate approaches, but is practical using the parabolic equation method.