Experiments on Drag Coefficients and Response of Wind Waves to Periodically Fluctuating Winds

Abstract

Experiments have been carried out to investigate drag coefficients and response of wind waves under periodically fluctuating winds. Wind stresses estimated from momentum conservation law considering radiation stresses were compared with those estimated from vertical distribution of wind speed. It is found that the former stresses are much larger than latter ones and about twice of the latter in the case of breaking wind waves. Vertical distributions of time-averaged wind speed of periodically fluctuating winds were also compared with those of constant wind speed. The significant difference between them can not be found. However, in the case of periodically fluctuating winds long period waves with predominant period of fluctuating winds were exited unlike constant wind speed.