Mechanism of drag coefficient saturation at strong wind speeds

Abstract

AbstractPrevious studies have demonstrated the saturation of drag coefficients at strong wind speeds. But the mechanism behind this saturation has not yet been fully clarified. In this study, at normal and strong wind speeds, we use a wind‐wave tank for investigating the peak enhancement factor of the wind‐sea spectrum, which is an appropriate wave parameter for representing interfacial flatness. We measured the water‐level fluctuation using wave gauges. At strong wind speeds, the result shows that the peak enhancement factor of the wind‐sea spectrum decreases with decreasing inverse wave age and with increasing wind speed. This suggests that the distinctive wind‐wave breaking occurs at strong wind speeds. It also suggests that this distinctive breaking of wind waves causes the saturation of drag coefficients at strong wind speeds.