ASA 124th Meeting New Orleans 1992 October

3aUW12. Geometric beam tracing.

Yong-Chun Liu

Michael B. Porter

Ctr. for Appl. Math. and Stat., New Jersey Inst. of Technol., Newark, NJ 07102

Despite their approximate nature, ray methods continue to play an important role in ocean acoustic modeling---sometimes there is no practical alternative, for instance, in modeling impulses or high-frequency sources in 3-D environments. Unfortunately, ray methods are prone to implementation difficulties which often degrade their accuracy. Problems include the failure to locate an eigenray (leading to artificial drop-outs), errors in tracking the phase change through a caustic or singularities at caustics. Gaussian beam methods have been proposed as a remedy; they lead to particularly simple codes free of these problems. However, the promise of Gaussian beam methods remains partially unfulfilled since the optimal choice of beam initial conditions is still being debated. A modified beam tracing algorithm is described that preserves the appealing structural simplicity of Gaussian beam tracing but sacrifices the caustic correction to obtain a robust algorithm. Plots of transmission loss show that the resulting model yields excellent agreement with more computationally intensive full-wave models.