A Two-Ended Shooting Technique for Calculating Normal Modes in Underwater Acoustic Propagation,
Abstract
An algorithm for the calculation of acoustic normal modes in the ocean is described. The algorithm is valid for an arbitrary sound speed and density profile in the water column and bottom. Losses due to volume absorption in the water and bottom, surface and bottom roughness. and shear waves in the bottommost layer can be calculated as perturbations. The essential feature of the algorithm is a two-ended shooting method in which the trial solution is started separately at the surface and bottom and numerically integrated to a matching depth in the middle, usually near the minimum sound speed. The trial solution is iterated until a continuous function with a continuous derivative is obtained. Shooting from both ends results in a more stable algorithm and gives more accurate eigenfunctions than are obtained using conventional single-ended shooting methods. This paper describes the theory and general numerical implementation of the algorithm. For completeness, equations are given for calculating group velocities, propagation loss in a range-dependent environment, and losses due to volume absorption, surface and bottom roughness, and shear waves in the bottommost layer. The two-ended shooting algorithm has been implemented in the computer program PROLOS, which has been used extensively at DREA since 1979. In this paper results of numerical computations will be presented, including the AESD Workshop Test Cases and comparison of predictions with some measured data from a shallow water propagation loss experiment. (Canada)
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1985
- Accession Number
- ADA161965
Entities
People
- Dale D. Ellis
Organizations
- Defence Research and Development Canada