Numerical Simulation Of The Slamming Effect Of Freak Wave On Three-dimensional Plate Structure

Freak wave is an extreme wave in the ocean with high wave height,concentrated energy,strong nonlinearity and frequent occurrence.It is precisely because of these characteristics of freak wave that when it slams on the marine structure,it will cause more damage to the structure.Some scholars at home and abroad have begun to explored the interaction between freak wave and two-dimensional structures,but research about the slamming effect of freak waves on three-dimensional plate structures is still lacking.A three-dimensional(3-D)numerical wave tank was constructed based on STAR-CCM+.Then the inlet of velocity method is used to generate fifth-order Stokes wave and freak wave based on the Peregrine breather solution model,and analyzing the mesh convergence of two waves to obtain two suitable meshing methods and the wave parameters agree well with the theoretical values.A numerical model of wave slamming on three-dimensional plate structures was established and verified.Comparing fifth-order Stokes wave and freak wave with the "same-scale",it is found that the wave surface elevation of freak wave is more "saturated",the velocity of water quality point is greater,and the surface contour is like a moving "water wall".Then analyzing the difference between the slamming effects on the bottom and front of three-dimensional plate by these two waves,and it is found that the slamming force,slamming pressure caused by freak wave on the bottom of plate are larger than fifth-order Stokes wave,which is related to the higher vertical velocity of water quality point and more slamming water volume;the slamming force,slamming pressure and relative wet ted area on the front of plate are greater,because the horizontal velocity of water quality point is greater and the front half of crest is steeper.Finally,the variation law of the slamming load on the bottom and front of three-dimensional plate with influencing factors was discussed one by one.Among them,as the focus position moves backward,the maximum slamming pressure position at the bottom of plate moves backward,and the slamming force,slamming pressure and relative wetted area on the front of plate decrease;as the relative air gap increases,the slamming force,slamming pressure and relative wetted area on the bottom and front all decrease;as the relative plate length increases,the slamming force,slamming pressure and relative wetted area on the bottom of plate gradually decrease,but the slamming force,slamming pressure and relative wetted area on the front all increase;as the angle of attack increases,the slamming force on the bottom of plate increases,while the slamming force on the front decreases.In the end of this thesis,the effect of freak wave slams on the semi-submersible platform was studied.Taking the HYSY-981 platform as an example,the slamming load of freak wave on the fixed platform was calculated and compared with three-dimensional plate with the same size as the platform deck.Then the slamming load and motion response of freak wave impacts on the floating platform was calculated,and analyzing the difference of slamming load between it and the fixed platform.This provides a feasible method for the numerical calculation of the slamming load on the semi-submersible platform by freak wave.