Calculation of underwater acoustic fields by Gaussian beam tracing

Abstract

The method of Gaussian beam tracing has recently received a lot of attention in the seismological community. In comparison to standard ray tracing, the method has the advantage of being free of certain ray tracing artifacts such as perfect shadows and infinitely high energy at caustics. The technique is especially attractive for high-frequency problems or problems with complex bathymetry where normal mode, FFP, or parabolic models are not practical alternatives. The Gaussian beam method associates with each ray a beam with a Gaussian intensity profile normal to the ray. The beam curvature and width are governed by an additional pair of differential equations that are integrated along with the usual ray equations to compute the beam field along the ray. Analytic solutions to the beam equations are available for certain canonical problems, including the cases where the sound speed or square of the index of refraction is a linear function of the space variables. Thus ray tracing codes that employ patches of such domains are easily adapted to the beam tracing method. We present an overview of the method and results for certain ocean acoustic scenarios, which illustrate the performance of the method.