Extreme waves and modulational instability: wave flume experiments on irregular waves

摘要

We discuss the formation of large amplitude waves for sea statescharacterized by JONSWAP spectra with random phases. In this context we discussexperimental results performed in one of the largest wave tank facilities inthe world. We present experimental evidence that the tail of the cumulativeprobability function of the wave heights for random waves strongly depends onthe ratio between the wave steepness and the spectral bandwidth. When thisratio, called the Benjamin-Feir Index, is large the Rayleigh distributionclearly underestimates the occurrence of large amplitude waves. Ourexperimental results are also successfully compared with previously performednumerical simulations of the Dysthe equation.