A Proposed Soliton Mechanism in Wind-Wave Surface Generation and Scattering
Technical rept. Nov 1985-Jun 1986
MIDDLETON (DAVID) NEW YORK
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Initially, to account for observed discrepancies in acoustic backscatter strengths and doppler shifts, and subsequently, to provide a plausible model of local wind-wave surface generation, a soliton mechanism has been proposed, which appears to play a critical role under the following operating conditions small grazing angles, high frequencies, and moderate strong wind speeds, in bubble-free regimes. Earlier versions of the proposed soliton surface, which is postulated to be a part of the wind-generated surface drift layer, are extended in this study to include the effects of surface tension, as well as many physical and analytical features. Surface tension is a dominant factor, setting a minimum thickness, he-min, of 5.5 mm, to the effective drift layer or channel which supports the soliton ensemble. Layer thickness 07-8 mm and soliton speeds 030 cms appear typical at mean near- surface wind speeds U sub infinity 10 ms. Key features of these solitons or hydraulic bumps one-sided waves, which comprise the high wavenumber components of the total surface, including the gravity-capillary structure on which the wind-generated soliton ensemble rides, are i their nondispersive nature, ii their independence, reflecting the fact that solitons can travel through one another without distortion and iii that they are in the unidimensional models limiting solutions of the Kortweg-de Vries equation.
- Physical and Dynamic Oceanography