ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

5aUW12. Pulse propagation in a range-dependent turbulent ocean.

W. R. Chang

S. H. Dong

J. H. Tarng

Dept. of Commun. Eng., Chiao-Tung Univ., Hsin-Chu, Taiwan

In this research, an acoustic pulse propagating in a turbulent ocean with slightly range-dependent vertical sound-speed profile is investigated. A numerical approach called the split-step method, based on the parabolic equation, is used to simulate each frequency component of the pulse to propagate through the ocean. A random phase screen is generated to include the effects of random fluctuation of sound-speed profile in each step. The average acoustic pulse profile and root-mean-square pulse width are evaluated for different fluctuation strengths and scale lengths of turbulence. Some results are compared with those computed by theoretical approach. It is found that in each realization the pulse echoes, due to the multipath propagation, are changed in arrival times, pulse shapes, and numbers because of the random fluctuation of the sound-speed profile. The broadening of the pulse width is varied for different depths of the receiving position. An initial Gaussian-shaped pulse is considered. For the simulations, a Gaussian-beam source is used instead of a point source. Here, the sound-speed profile is assumed to be changed uniformly in the range direction.