Study Of Nonlinear Wave Forces On Breakwaters With Box-type Structure Suction Foundation

In this paper, the nonlinear standing wave forces on box-type suction foundation breakwaters are investigated by a time-domain second-order method, using three dimensional Laplace Equation as governing equation, and second-order Stokes waves as incident waves.In the beginning, the velocity potential and displacement of incident waves and reflected waves are separated respectively. Based on time-domain second-order theory, first and second-order wave reflection models are established by using Taylor series expansion and perturbation expansion. In the model, the free surface conditions are satisfied at still water to make the computational domain time invariant.Reflection models are calculated by using GID software as the preprocessor and postprocessor, the program as the solver, and finite element method as the numerical solution method.In the solving process in time domain, fourth-order explicit scheme of Adams Bashforth is taken to calculate the velocity potential and displacement of reflected waves at free surface and an artificial damping layer is adopted as the far field radiation condition to avoid the wave reflection from the outer boundary. In addition, Smooth function is adopted in body boundary condition to avoid unstable wave fields and second-order wave force theory is used to calculate first and second-order wave forces.Using reflection models, first and second-order standing wave forces on vertical wall and continuous arched wall are studied respectively. In the study of the standing waves on vertical wall, wave forces and wave displacements under different aging times and the distribution of wave pressure in vertical direction have been investigated and verified. Then, characteristics of standing waves on vertical wall are obtained. At last, the results have been compared with the ones obtained from standard methods.On the basis of the investigation of nonlinear wave forces on vertical wall, nonlinear wave forces on arched wall have been studied and the results have been verified by comparison with experiments. Finally, the results are compared with the ones of vertical walls. It is showed that the distribution of the wave pressure as well as the changing with time of wave forces and displacements has the same trend with vertical wall, which proves that the continuous arched wall has stronger resistance to wave force than vertical wall.