The Implementation Of GRAB Algorithm

The research on the underwater sound propagation is the foundation to understand and explain the underwater acoustic phenomenon. There are two kinds of acoustic field models. One is the range-independent model and the other is range-dependent model. The former assumes the ocean environment is horizontally stratified, and the latter consider the change of sound velocity and sea bottom topography change with range, which is more useful sound field calculation in the complex ocean environment. GRAB (Gaussian Ray Bundle) is a ray theoretical model introduced in 1996 that allows the rays to have a "width", that is, a Gaussian spread of energy in depth about the central ray path. It is a range-dependent acoustic field model. To some extent GRAB is a approximation method of Gaussian beam model.GRAB algorithm is implemented based on the program package bellhop in this paper. GRAB calculates eigenrays and TL in very easy way and then has high computational speed. GRAB computes TL through a user-defined model include source location, wave frequency, distance of transmission and so on. The result is compared with result obtained with other method. The compared results prove that this method is feasible.At last, some example were calculated in the paper, and several advices were given for improving the arithmetic.