Acoustic Modeling Using a Three-Dimensional Coupled-Mode Model.

摘要

The objective of this work is to gain an understanding the physics of propagation in continental shelf areas, specifically horizontal refraction and mode coupling induced by three-dimensional (3D) inhomogeneities in the waveguide. A coupled-mode approach has been applied for this purpose. The coupled-mode approach is attractive for solving problems involving 3D propagation for several reasons. First, this technique provides intuitive results for understanding the features responsible for observed propagation effects in range-dependent environments. For example, upslope propagation is characterized by acoustic energy radiated into the bottom at discrete depths associated with mode cut-off. The modal decomposition of the acoustic field has also been used to describe horizontal refraction in a wedge-shaped ocean, for which the single-mode interference pattern associated with rays launched up and across the shelf has been well documented Weinberg and Burridge (1974). Furthermore, coupled-mode solutions can be highly accurate and have been used for benchmarking solutions to range-dependent problems Jensen and Ferla (1990). In order to appreciate the limitations of existing 3D models, it is necessary to have methods which can provide reference solutions for comparison.