Preliminary Investigation on the Effects of Gusty Wind Forcing on Steep Unidirectional Waves

In air-sea interaction, wind, the driving force that generates surface waves, exchanges energy and momentum with waves. However, the airflow with high turbulence intensity above the waves leads to the evolution of nonlinear waves being more complex. Therefore, it is crucial to investigate the role of wind-wave interaction in wave evolution and consequent extremewave generation. In this paper, the parametric laboratory experiments were carried out at Shanghai Jiao Tong University to investigate the effect of wind-wave interaction on nonlinear wave evolution and extreme wave generation. Here, we are concerned with wave-by-wave local interactions different from the existing work on wind energy transfer in the spectral wave model. We considered three sets of random waves generated from the JONSWAP spectrum with different initial steepness. The wind with high turbulence intensity is generated by a movable fan array in the large-scale open wave tank. We investigate the long-time nonlinear wave evolution with wind and discuss the statistical properties of waves. We find that the gusty wind forcing enhances the 'heavy tail' effect in the exceedance probability of wave height. It suggests that the gusty wind forcing leads the nonlinear waves to deviate from equilibrium, increasing the probability of extreme events.