RESONANT EVOLUTION OF LONG PERIOD WAVES BY PERIODICALLY FLUCTUATING WIND VELOCITY

This paper investigates the spectral characteristics of low frequency fluctuations of natural wind velocity and atmospheric pressure, and the resonant evolution of long period waves by low frequency fluctuations of winds in a laboratory experiment. Laboratory experiments on the responses of wind waves under periodically fluctuating winds have been conducted to find an alternative generation mechanism for long period waves. The experiments show that the long period waves developed at the peak frequency of the low frequency fluctuations of wind speed and air pressure. Through the spectral analysis of fluctuating components of wind speed, air pressure and water surface elevation, the long period waves are found to be generated and resonantly developed by the fluctuating components of surface shear stress due to periodically fluctuating wind speed.