A Proposed Soliton Mechanism in Wind-Wave Surface Generation and Scattering
Abstract
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 0(7-8 mm) and soliton speeds 0(30 cm/s) appear typical at (mean) near- surface wind speeds U sub infinity 10 m/s. 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.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 19, 1986
- Accession Number
- ADA179918
Entities
People
- David Middleton