Research on the statistical characteristic of freak waves based on observed wave data. (1st January 2022) - Ji, Xinran
Abstract: Freak waves are characterized by high wave, great destructive power, abrupt behavior, and a significant threat to offshore structures. In this study, the observed wave data of multiple sea areas are utilized, the relation between the occurrence of freak waves at real sea states and the statistical characteristics of wave trains are investigated, and the probable reasons for freak wave generation at real sea conditions is explored. It can be found that for the wave trains with higher kurtosis, the occurrence probability of huge wave height is underestimated by the Rayleigh distribution. It can be accurately predicted by the MER distribution and GC distribution. Generally, the occurrence probability of freak wave increases linearly with the increase of kurtosis from the statistical results, and the MER model is capable of describing the relation between occurrence probability of freak wave and kurtosis. Moreover, the generation types of freak waves are analyzed based on the wavelet energy spectrum and time process of wave surface for typical freak waves in the observation data. Freak waves at real sea states are attributed to the modulation instability and wave energy superposition. Highlights: Observed wave data of multiple locations are utilized to investigate the statistical characteristics of freak waves. The occurrence probability of the observed freak waves is higher than that in the Rayleigh distribution. The MER distribution can better predict the occurrence probability of freak waves in real sea states. Generation mechanism of freak waves are attributed to modulation instability and wave energy superposition.