Effects of Stable and Unstable Surface-Water Stratifications on Scalar Transfer across a Wind-Driven Air-Water Interface.

Abstract

The effects of stable and unstable thermal stratifications on both scalar transfer across the wind driven air water interface and turbulence structure were investigated through laboratory experiments in a wind-wave tank. The steady stable and unstable thermal stratifications were generated in the wind wave tank by supplying cold and hot waters into the upper and lower parts of the tank. Instantaneous streamwise and vertical velocities and temperature in the water flow were simultaneously measured using a laser Doppler velocimeter (LDV) and a cold film I-probe operated by a constant-current temperature bridge. The results show that the turbulence quantities in the stratified layer are strongly affected by buoyancy. However, the turbulence quantities just beneath the air water interface and the frequency of the appearance of large-scale surface-renewal eddies that dominate heat and mass transfer across the air-water interface were not affected by the stable and unstable thermal stratifications. The facts suggest that the stable and unstable stratifications in the interfacial water flow do not play an important role in the heat and mass transfer across the wind driven air water interface.