Research On Extreme Wave Run Up On Vertical Structures

Vertical structures are common engineering structure in marine construction.Wave run up on the vertical structure is a common physical process.Extreme wave run up is defined when the elevation of wave run up is greater than 2 times amplitude of incident wave.Extreme wave run up may cause casualties,structural damage or even loss of structural function.Therefore,the effect of wave run up needs to be considered for the safety design of vertical structures.However,Extreme wave run up of vertical structures is not considered in the current design code.In this paper,a three-dimensional numerical wave tank based on a fully non-hydrostatic free surface flow model is established,to carry out relevant numerical simulation experiments on the normal and oblique incidence regular wave run up on a vertical structure.Two different types of extreme wave run up phenomena are studied,and the effects of wave steepness,water depth and incident wave angle on wave run up are systematically studied.Due to the third-order resonant interaction,extreme wave run up is generated on the vertical structure when the wave is normally incident and interacts with the vertical structure.It is found that the variations of wave run up along the vertical plate are discrepant in different wave steepness and water depths.Firstly,the maximum amplification of wave run up increases with the wave steepness and water depth.Then,the tendency of maximum amplification of wave run up to move to the inner side of the vertical plate becomes more and more significant with the wave steepness and water depth increasing.Most important of all,the largest wave surface elevations at the weather side on vertical plate can reach up to about 4 times of the incident wave,much larger than the 2 times predicted from linear theory.When wave is incident less than critical angle,in addition to incident and reflected waves at the vertical wall,there is third wave developed along the wall,called the Stem wave,and the wave's phenomenon is called Mach reflection.Therefore,extreme wave run up of obliquely incident regular wave on vertical wall is studied,and this part mainly studies the effects of incident wave angle,wave steepness and water depth on wave run up.Firstly,the effect of incident wave angle is considered.The amplification of wave run up at the vertical wall increases monotonously,and the amplitude growth rate of Stem wave increases linearly with incident angle when the angle is less than 20°.The location of maximum the amplification of wave run up decreases with increasing incident angle.The width of Stem wave decreases with increasing incident angle.A typical standing wave pattern will appear along the normal to the vertical wall when the incident angle is large.Next,the effect of wave steepness is considered.When the incident angle is small,the amplification of wave run up along the wall increases strictly with the wave steepness.As the incident angle increases,the dependence of the amplification of wave run up on the wave steepness decreases.The growth rate of the amplification of wave run up decreases with wave steepness increasing,while the Stem wave width increases.Then,the effect of water depth is considered.When the water depth is from shallow to finite water depth,the amplification of wave run up along the wall increases with the decrease of relative water depth,but the width of Stem wave increases with the increase of relative water depth.The maximum amplification of wave run up and the width of the Stem wave remain at a constant value in deep water conditions.The results show that the extreme run up of the normal or oblique incidence of regular waves on the vertical structure is greater than the linear theory predicted 2 times.Therefore,it is necessary to take into account the effect of nonlinear wave run up for the safe design of vertical structures.In addition,this paper studies the extreme wave run up on vertical structures.Based on the influence of wave run up,it can provide technical support for the safe design and reasonable location of vertical structures.