Finite element modeling of longitudinally invariant shallow water waveguides.

Abstract

Finite element models of shallow water waveguides are fully customizable to include effects such as range dependent bathymetry, sound speed profiles, and interface roughness. However, until recently, these solutions have been confined to 2-D environments. While these models provide benchmarks for other solution methods such as coupled modes or parabolic equations, they cannot be compared with data. Fully 3-D models of shallow water waveguides are still beyond current computational capability, but longitudinally invariant models may bridge the gap. These solutions are often known as 2.5D models. In this scheme, the waveguide is reduced to a series of 2-D finite element domains, the solutions to which comprise the Green’s function in the wavenumber-frequency domain of the 2.5D space. A cosine transform is then used to convert these into a frequency-domain solution for a longitudinally invariant space. In this study, the wavenumber-frequency Green’s function will be analyzed in order to develop more efficient computational methods for shallow water waveguides. Solutions for both flat and rough interface shallow water waveguides in 2.5D will be presented and compared with a wavenumber integration approach. [Work supported by the Office of Naval Research, Ocean Acoustics Program.]