Numerical Simulation Of Wave Forces On Horizontal Plate Under Freak Waves

Wave impact force is a traditional and at the same time frontier problem,because new challenges are constantly emerging with the deepening awareness of marine environment.Freak wave which has been widely concerned about in recent years is one of them.It is a kind of extreme wave with high wave height,and will cause great damage to the marine structures and the ships.Although some scholars at home and abroad have carried out research on the interaction between freak waves and structures,it is mostly limited to the cylinder structures and hull structures.So the systematic research on the wave forces acting on the plate structure induced by freak waves has yet to be developed.Firstly,a numerical wave tank based on the VOF method was established,which can make the freak wave occurred at the assigned time and place.And then the mechanical characteristics of simple plate and bridge superstructure induced by freak waves was studied.The main results are as follows:(1)With the help of the existing theoretical models,the numerical wave environment was established successfully,which can make the freak wave occurred at the assigned time and place.And it was found that the results not only satisfy the strict definition of freak wave,but also keep agreement with the target wave train.There is a big difference between the freak waves and the equivalent-size regular waves on the process of acting on the simple horizontal plate,the ratio of their maximal impact pressure is nearly 1.13,if a third of the peak impact pressure or the average one which are more stable taken as the characteristic value,the ratio can reach 1.63 and 1.90.Thus,The freak wave is more harmful.(2)In this paper,the impact pressure of the simple horizontal plate induced by freak waves is closely related to the focusing position of freak waves,the clearance under the plate and the width of the plate.Different from the randomness of impact pressure induced by regular wave,the plate has the most dangerous area(focusing position)induced by freak waves.When the focusing position in the center of plate,the peak impact pressure under the plate is maximal,behind the plate followed by,in the front of the plate is minimal.The peak impact pressure under the plate firstly increases and then decreases with the clearance increasing,and the maximum appears in the relative clearance ?h/H=0.17.When the focusing position of freak wave is in the center of plate,the peak impact pressure under the plate increases with the increase of the width of the plate.The maximal impact pressure and the maximal uplist force is not in the same condition.(3)In this paper,the impact force of bridge superstructure induced by freak wave increases with the increase of wave height,but the local impact force at the side of head sea,the maximum horizontal force and the maximum moment are very sensitive to the changes of impact angle of freak waves.Compared to the girder of T-beam bridge and T-shaped box girder,fish-bellied box girder has obvious advantages in resisting wave load.