Analysis of statistical characteristics of freak waves based on High Order Spectral coupled with CFD method

Freak waves, which are characterized by their large wave heights and significant energy, can severely damage marine structures. The evolution of these freak waves is nonlinear, making it difficult to describe them with basic wave parameters. This paper analyzes the statistical characteristics of freak waves during the evolution. The freak waves are generated in a physical wave tank based on the two-wave train superposition method. An advanced coupled High-Order Spectral methods (HOS) and viscous Computational Fluid Dynamics (CFD) method is proposed to generate high quality freak waves. As the results of numerical methods agree well with the experimental results, the correlation between the statistical characteristics and freak wave mechanism is provided. The results reveal that the kurtosis of freak waves is related to the maximum wave crest, while the skewness is both influenced by the maximum wave height and the stream velocity at the wave crest. The wave propagation mechanisms are analyzed by Empirical Mode Decomposition (EMD). The results show that the location with the largest energy in low-frequency region sometimes occurs after the peak wave height, which may cause drift motion of floating structures and lead to hazards.