Wind speed scaling and the drag coefficient

Wind speed scaling in similarity law in wind-generated waves and the drag coefficient are studied.In analyzing the data in the wind wave channel,it is found that the u^* scaling greatly reduces the scatter in the U₁₀ scaling.The u^* scaling has much less scatter than the scaling using other wind speeds.The friction velocity seems to play a distinctive role in wave growth.The result is important in the applications of the similarity law and in wave modeling.In theory it gives an insight into the mechanism of wind wave interaction.It is found that wave steepness is important in influencing the drag coefficient.The variability of the coefficients in the currently widely used drag form can be explained by the differences in wave steepness in the observations.A drag coefficient model with wind speed and wave steepness as parameters is proposed.An explanation for Kahma's result that the u^* scaling does not reduce the scatter in the U₁₀ scaling is given.