3aUW12. Estimation of nonlinear effects in global scale ocean acoustic propagation.

Session: Wednesday Morning, May 15

Time: 11:20

Author: B. Edward McDonald
Location: Naval Res. Lab., Washington, DC 20375


The nonlinear progressive wave equation (NPE) [B. E. McDonald and W. A. Kuperman, J. Acoust. Soc. Am. 81, 1406--1417 (1987)] is used to derive quantitative estimates for the magnitudes and characteristic features of nonlinearities generated by finite amplitude acoustic signals during propagation across ocean paths of global scale. Nonlinear effects accumulate over long propagation paths, and are accentuated at convergence zone caustics. The goals are to estimate (1) levels of harmonic generation in ocean tomographic experiments and (2) waveform steepening in underwater explosions. Harmonic generation (1) is estimated from a linear baseline solution involving vertical eigenmode expansion. The result implies second harmonic magnification at odd numbered convergence zone ranges. Waveform steepening (2) is estimated by time-domain numerical integration and related to modal excitation differences in the far field [J. Ambrosiano, D. R. Plante, B. E. McDonald, and W. A. Kuperman, J. Acoust. Soc. Am. 87, 1473--1481 (1990)]. [Work supported by ONR.]

from ASA 131st Meeting, Indianapolis, May 1996