Three-dimensional propagation and scattering around a conical seamount

Abstract

A three-dimensional (3D) propagation and scattering model is developed for an offset acoustic source in an ocean with axisymmetric bathymetry. Based on the same theoretical foundation as the formulation presented by Taroudakis [M. I. Taroudakis, "A coupled-mode formulation for the solution in the presence of a conical sea-mount," J. Comput. Acoust. 4, 101-121 (1996)], the present approach combines a spectral decomposition in azimuth with a coupled-mode theory for two-way, range-dependent propagation. However, the earlier formulations were severely limited in terms of frequency, size, and geometry of the seamount, the seabed composition, and the distance between the source and the seamount, and were therefore severely limited in regard to realistic seamount problems. Without changing the fundamental theoretical foundation, the present approach applies a number of modifications to the numerical formulation, leading to orders of magnitude in numerical efficiency for realistic problems. Further, by using a standard normal mode model for determining the fundamental modal solutions and coupling matrices, and by applying a simple superposition principle, the computational requirements are made independent of the distance between the seamount and the source and receivers, and dependent only on the geometry of the seamount and the source frequency. Therefore, realistic propagation and scattering scenarios can be modeled, including effects of seamount roughness and realistic sedimentary structure.