EXPERIMENTAL-STUDY OF NON-LINEAR WAVE-WAVE INTERACTION AND WHITE-CAP DISSIPATION OF WIND-GENERATED WAVES

An experimental scheme was designed to obtain laboratory-scale verification of Hasselmann's nonlinear wave-wave interaction and white-cap dissipation theories. Water wave height and fluctuating air pressure were measured simultaneously in a fixed reference frame as a function of fetch in the Stanford Wind, Water-Wave Research Facility under the conditions of a steady wind and a stationary wave spectrum. All the data were obtained 5 mm above the highest point of the wind waves for five stations (3 m apart on average) and at three wind speeds (7.1, 8.0 and 8.9 m/sec). The wave height and fluctuating pressure were measured by a capacitance wave-height gauge and a crystal pressure transducer, respectively. Based on the experimental results, Hasselmann's nonlinear wave-wave interaction theory appears to be valid. Barnett's approximate parametric equation for calculating the energy transfer of nonlinear wave-wave interaction and Hasselmann's white-capping dissipation model were also verified and appeared to be applicable in the relatively low and intermediate frequency region of a wave spectrum for a normalized fetch range of 100-500. Based on the results of an overall energy balance in a gravity wind-wave spectrum, the nonlinear wave-wave interaction mechanism is shown to play a dominant role in the energy transfer processes after the wave spectrum is generated. © 1979.