High-frequency acoustic scattering from stratified turbulence

Abstract

A laboratory study of high-frequency acoustic scattering from stratified turbulence was performed in order to test the theories and techniques used for the prediction of acoustic scattering. Scattering predictions were made with a computer simulation code which incorporates Lane's hydrodynamic model of stratified turbulence with the relevant aspects of linear scattering theory. Laboratory acoustic measurements were made for a range of acoustic system parameters, including forward scatter in the vertical and horizontal planes, and vertical backscatter. Hydrodynamic characterization of the sound speed spectrum was made with traversing conductivity probe arrays and with quantitative optical shadowgraphs; the data were then used to define the turbulence model parameters. The analytical techniques used to extract the hydrodynamic model parameters from both conductivity and shadowgraph data gave consistent results, and verified the Lane model as a valid descriptor of stratified turbulence. Theoretical acoustic scattering level predictions made with the simulation code are in good agreement with the laboratory acoustic measurements. These results verify the laboratory measurement techniques and validate our implementation of linear scattering theory and Lane's turbulence model for predicting acoustic scattering from stratified tubulence. [Work supported by Navy SSPO and Dynamics Technology internal R&D funding.]