A numerical study on the characteristic flow structures of a micro-breaking wind wave

Abstract

We present results from numerical simulation of an aqueous turbulent boundary layer underneath a dynamic air-water interface and driven by wind stress and pressure. The simulation results reveal distinct surface and flow structures of micro-breaking wind waves including a bore-like crest preceded by parasitic capillary waves riding along the forward face and elongated streamwise velocity streaks in the backward face, and confirm the observations in the laboratory and field experiments. The results also highlight the potential impacts caused by the short-wavelength capillaries on the gravity dominant free-surface flows, and consequently reveal the necessity in incorporating such microscale processes in the parameterizations of fluxes across the air-sea interface.