DEVELOPMENT AND EVALUATION OF EQUIVALENT-FLUID SEABED MODELS

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Authors
  1. Li, J-F.
  2. Hodgson, M.
Corporate Authors
Defence Research Establishment Atlantic, Dartmouth NS (CAN);British Columbia Univ, Vancouver BC (CAN) Dept of Mechanical Engineering
Abstract
Sound reflection from the seabed is very important in the study of sound propagation in shallow water. As most seabeds support both compressional and shear waves, seabed rigidity affects the reflection loss and phase shift of the bottom reflection. In this case the problem of modelling sound reflection from the seabed becomes more complicated. An approximate method is to replace the solid with a fluid by choosing suitable seabed parameters. This replaced fluid is termed the equivalent-fluid seabed. The objective of this report is to develop and evaluate equivalent-fluid seabed models. A literature review has been done and a bibliography provided. Existing equivalent-fluid seabeds have been programmed and evaluated by calculating the reflection coefficient of the bottom. Meanwhile, shear-wave effects on reflection have been studied. A new effective-seabed model is proposed from the calculation of the effective impedance of the seabed. This model is evaluated numerically. Comparison of the new model with the existing model shows that the new model agrees better with the solid seabed. Furthermore, grazing-angle-dependent parameters of the equivalent-fluid seabed are proposed. It is shown that the use of the grazing-angle-dependent parameters gives the best agreement with the values for the real seabed in the prediction of the reflection coefficient.
Keywords
Shear waves;Grazing angle;Acoustic reflection;Reflection loss;Seabed;Acoustic impedance
Report Number
DREA-CR-97-421 — Contractor Report
Date of publication
01 Mar 1997
Number of Pages
41
DSTKIM No
97-03783
CANDIS No
503813
Format(s):
Hardcopy;Document Image stored on Optical Disk

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