Numerical Simulation Of Freak Waves In Three-Dimensional Wave Field

In present paper,a numerical simulation of freak wave in three-dimensional wave field is established.The method based on relevant experience formula of frequency spectrum and directional spectrum makes a superposition on composition wave of different amplitudes, frequencies and directions to generate random wave,and superposes a basic random wave train with a transient wave train to generate a wave train containing a freak wave.The main simulation results are as follow:·The numerical model of freak wave in three-dimensional wave field by two wave trains superposition method can simulate the freak wave at certain time and certain location,and simulate the natural recorded freak wave effectively.·The directional distribution of wave energy plays a significant role in the generation of freak wave.Since the directional distribution of wave energy is introduced,the wave height of the simulated freak wave is increased significantly.So that the freak wave is generated With less percentage of energy in transient wave train when compared with two-dimensional wave field.Such as the simulation of "New Year Wave",the percentage of energy in transient wave train p₂ is respectively 20%in two-dimensional wave and 11.2%in three-dimensional wave when reach the same simulation effect.·Both the percentage of energy and the spectrum width have a effect on the simulation of freak wave in three-dimensional wave field.The effect of unimodal spectrum types is less than the effect of percentage of energy on the result of simulated freak wave;In the range of the spectral peak heightS₁/S₂ is 0.5～2.0 and the peak frequencyω₂/ω₁ is 1.2～4.0,the bimodal spectral characteristic parameters play a significant role in the generation of freak wave.However,the effect on freak wave form is very small when the spectrum total energy is a certain value.·The P₂ corresponding to bimodal spectrum is less than the P₂ corresponding to unimoda spectrum in three-dimensional wave field.The conclusion given by Chien that occurrence possibility of freak waves may increase in the wave field of bimodal spectra is confirmed from one side.