Study On Overtopping Characteristics Of Artificial Revetment On The Steep-sloped Step Based On SPH Method

With the development of construction projects on coral islands in South China Sea,hydrodynamic characteristics of wave transformation over the coral reefs have attracted more and more attention.When the wave propagates from the deep sea to the reef-flat,the deformation in shallow water occurs along the reef-face,what' more,the wave breaks on the reef-rim or reef-flat,which will cause the further wave set-up on the reef-flat.The rise of water level increases the risk of overtopping at the structure on the reef-flat.studies of wave transformation,wave breaking and wave overtopping can provide references for the design of protective structures on the reef-flat.Based on the weakly compressible smoothed particle hydrodynamics(WCSPH)method,a numerical model is established to simulate solitary wave interaction with the artificial revetments on the reef-flat.Navier-Stokes equations are used as the control equations in the model,and additional dissipation term is added to the continuity equation,which suppresses the unphysical pressure oscillation.In order to prevent fluid particles penetrating solid boundaries,the pressure of boundary particles is calculated using the improved boundary condition generated by dynamic particles.The processes of solitary waves overtopping dams are simulated under different wave heights and front slope angles.A good agreement is obtained between the numerical and experimental results on the wave surface,overtopping and maximum wave overtopping depths,indicating the present SPH model can accurately simulate the process of solitary waves overtopping dams.Later,the model is further verified by comparing with the experimental results of solitary wave transformation over the simplified coral reefs.The verification results indicate that the model can accurately simulate the process of solitary wave transformation over the simplified coral reefs.The idealized model of the coral reefs consists of a steep slope and a horizontal flat.By numerical simulation,the propagation and overtopping process is studied during solitary waves propagating process over the artificial revetment structures on the steep-sloped step.The influences of slopes and horizontal flat lengths on wave propagation and overtopping are studied under different wave heights,water depths and breast wall heights.The numerical results indicate that the wave overtopping increases first and then decreases with the decreaseof slope,which is influenced by the variations of reflected wave heights and wave breaking point.As the slope decreases,the breaking point moves towards the incoming offshore side,which is more obvious with the smaller relative wave height.In addition,the spatial distributions of wave height indicate that wave height is almost not affected by the slope when the wave moves to the horizontal flat,but which is controlled by the water depth.The numerical results indicate that the wave overtopping increases first and then decreases with the increase of horizontal flat length.Compared with the breast wall built on the top of the slope,the wave surface at the breast wall will rise faster and the maximum wave overtopping depths will be greater in the process of wave overtopping when there is a small horizontal flat in front of the breast wall.