The Effects of Surfactants on Breaking Wind Waves

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0221335 DuncanIt has been observed that the rate of gas transfer across the air-sea interface correlates well with the mean squared slope of the high frequency surface waves. It has also been noted that the presence of surfactants, at concentrations that have almost no effect on surface tension, dramatically reduces the high frequency components of the wind wave spectrum. Wave tank studies of wind waves, and wind waves plus mechanically generated waves, with and without soluble surfactants, will seek to understand the mechanisms for this reduction in mean squared slope in the presence of surfactants, as well as the characteristics of high frequency waves. At low concentrations, it is hypothesized that the effects may result from the concentrating of surfactants at the wave crests, where capillary effects are typically largest. A variety of laboratory measurement techniques will be used. A cart carries measurement devices along the wave tank at speeds commensurate with the wave phase. Second Harmonic Generation techniques allow dynamic measurement of surfactant concentration. For these latter studies, the system will be at a fixed location and randomly sample the wind waves.