Numerical Study Of The Slamming Effect Of Freak Waves On Marine Engineering Structures

As a kind of strong nonlinear wave,freak wave can do great harm to marine engineering structures.Due to the increasing number of marine accidents caused by freak waves in recent decades,it has attracted more and more attention.At present,scholars have done a lot of work on the formation mechanism,generation model and its interaction with simple structures,etc.Based on the existing research progress,this paper further studies its slamming effect on three-dimensional plate and on typical Marine engineering structure ships.In this paper,the numerical flume of wave is established by using STAR-CCM+,and the freak waves of linear regular waves,fifth order Stokes waves and first order Peregrine respiratory solutions are simulated respectively.The numerical solutions are in good agreement with the theoretical solutions.Based on the numerical simulation of wave,the slamming interaction model of wave and three-dimensional plate was established,and the numerical model was verified by reproducing two experiments of wave and plate slamming interaction.On this basis,the variation law of the slamming load on the bottom of the plate caused by the freak wave and the fifth order Stokes wave with the height of the air gap,the length of the plate and the height of the wave peak,the similarities and differences of the two impacts on the plate,and the variation law of the slamming load caused by the freak wave with the focusing position are analyzed.By analyzing the numerical results,it is found that the air gap height has a great influence on the slamming load at the bottom of the plate.The maximum slamming vertical force and the maximum slamming pressure at the bottom of the plate both decrease with the increase of the air gap height under the action of either the deformed wave or the fifth-order Stokes wave.The maximum slamming vertical force and the slamming pressure of the freak wave on the bottom of the plate are greater than that of the fifth order Stokes wave.The plate length has little effect on the impact between the two waves and the plate.The overall variation trend of the impact pressure time history curve in most working conditions is basically the same,but the impact pressure time history curve is different in some working conditions.The peak height has a great influence on the slamming load at the bottom of the plate.The maximum slamming vertical force and the maximum thump pressure at the bottom of the plate increase with the increase of the peak height no matter under the action of the freak wave or the fifth-order Stokes wave.Focus location of freak wave on a flat plate at the bottom of the slamming load has a certain influence,when freak wave focusing distance of plate end has a certain distance,flat bottom slamming vertical force and slamming pressure significantly decreases,and when the freak wave focus position is located in the flat position of front-end and back-end,slamming pressure is bigger than the maximum negative pressure value of the other conditions.Finally,the slamming effect of freak wave and the fifth order Stokes wave on the ship is calculated.Through the analysis of the numerical results,the following conclusions are drawn:the slamming load and the slamming process time of the fifth order Stokes wave on the fixed ship are greater than that on the floating ship;The slamming load and slamming process time of the first order Peregrine breathing wave on the floating ship are both larger than those on the fixed ship.For both fixed and floating ships,the slamming load value and the slamming course time of the freak waves are greater than that of the fifth order Stokes waves.At the measuring point with the largest difference in the slamming load value,the slamming load caused by the freak waves reaches 2.03 times that of the fifth order Stokes waves.In the slamming process between the two and floating ships,the motion response value caused by the freak wave is also greater than that of the fifth order Stokes wave.Thus,the threat of freak waves to ships is greater than that of the fifth-order Stokes waves.