SEA SURFACE SHEAR LAYER AND AIR-WATER MOMENTUM TRANSFER IN THE INITIAL STAGE OF WIND-WAVE GENERATION

Abstract

 This paper presents mechanical features of transitional air-water momentum and energy transfers in initial growing wind waves on the basis of the fluid flow statistics observed in wind-wave tunnel experiments. In the initial waves with short fetch, superpositions of capillary waves on the crest of gravity waves generate significant vorticity and transport it downward, resulting in a thick momentum boundary layer containing organized vortices. As the capillaries attenuate in growing wind-driven current via wave-current interaction, with increase of fetch, vorticity generation also attenuate and thus the thickness of the boundary layer decrease.