Faculty Advisor

W.W. Durgin

Faculty Advisor

M. Demetriou

Faculty Advisor

D. Olinger

Faculty Advisor

M. Padmanabhan

Faculty Advisor

M. Richman

Abstract

A predictive methodology for received signal variation as a function of ocean perturbations is developed using a ray-based analysis of the effects of internal waves and ocean turbulence on long and short range underwater acoustic propagation. In the present formulation the eikonal equations are considered in the form of a second-order, nonlinear ordinary differential equation with harmonic excitation due to an internal wave. The harmonic excitation is taken imperfect, i.e., with a random phase modulation due to Gaussian white noise, accounting for both chaotic and stochastic behavior. Simulated turbulence is represented using the potential theory line vortex approach. Simulations are conducted for long range propagation, 1000km, containing internal wave fields with added deterministic effects and are compared to those fields with non-deterministic properties. These results show that long range acoustic propagation has a very strong dependence on the intensity of deterministic fluctuations. Numerical analysis for short range propagation, 10km, was constructed for sound passage through the following perturbation scenarios: simulated turbulence, an internal wave field, and a field of internal waves and simulated turbulence combined. Investigation over varied initial conditions and perturbation strengths suggests internal wave environments supply the majority of spatial variation and turbulent eddy fields are primarily responsible for delay fluctuation. Spectra of the variations in mean travel velocity reveal internal wave dominance to be dependent on the intensity of the wave.

Publisher

Worcester Polytechnic Institute

Degree Name

MS

Department

Physics

Project Type

Thesis

Date Accepted

2006-03-09

Accessibility

Unrestricted

Subjects

ray chaos, eikonal equations, turbulence, Underwater acoustics, Ocean tomography, Eikonal equation

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