NONLINEAR WAVE GROUP INTERACTION IN THE LONG -TIME WAVE EVOLUTION PROCESS

Freak waves are a sudden nonlinear extreme wave disaster that seriously threatens people's lives and the safety of offshore structures. The occurrence of freak waves is generally accompanied by wave groups (Trulsen,2000; Slunyaev et al., 2006; Tang et al., 2019). In order to investigate the characteristics of wave groups and freak waves during the long time wave evolution process, the High-Order Spectral method (HOS) is adopted, and the modulated Stokes wave train is used as the initial conditions. Characteristics of wave groups are analyzed under different evolution stages and generation mechanisms. Furthermore, largest Lyapunov Exponent, correlation dimension and Kolmogorov entropy are used to calculate the nonlinearity levels at different time scales during long time wave evolution process. This provides a theoretical basis for the generation and prediction of freak waves.