Modeling three-dimensional propagation in a continental shelf environment using the finite element method

Abstract

Horizontal refraction is a well known three-dimensional propagation effect in underwater continental shelf environments. However, only a few experimental observations of this phenomenon exist. In 2007, horizontal refraction was not only experimentally verified off the coast of Florida but was found to dominate the acoustic propagation. Numerical models that allow for azimuthal variations in the geometry are needed to accurately model this environment. In this work, a three-dimensional finite element method with the longitudinally invariant technique is presented. In this method, a cosine transform is applied to the three-dimensional Helmholtz equation to remove the range-independent dimension. The finite element method is used to solve the transformed Helmholtz equation for each out-of-plane wavenumber. The inverse cosine integral is then used to transform the pressure field back to three-dimensional spatial coordinates. The computed pressure field is then suitable for comparison to experimental measurements. [Work supported by ONR, Ocean Acoustics.]