The Study Of Overtopping On Sloping Breakwater Based On The Wave Model By Coupling With The BEM And The VOF Method

With the rapid development of the computer and the numerical method for the fluid mechanics, the modern numerical simulation technology has been widely used. The numerical simulation method has many merits, such as low cost, comprehensive information and flexible calculation. Thus, the numerical simulation has became an important way to study the hydrodynamic of gravity waves. At present, many numerical models have been established; however, every model has its limitations. For example, very large calculation domains should be modeled in many studies, but we only consider some detail characteristics for some particular parts. For these cases, coupling numerical models are desired. The coupling numerical models can comprehensively descript wave fields with higher accuracy calculation. In addition, it can simulate some of the changes that we are concerned. Meanwhile, another numerical model is adopted to simulate the peripheral wave fields. The coupling models not only can obtain the detail of the wave fields and improve the overall computational efficiency, but can expand model applicable scope. Therefore, development a coupling model has important scientific value and practical significance.Based on the0-1type BEM model and the VOF method, the following items have been carried out:First of all, the0-1type BEM model and the VOF model are established respectively. Using the Laplace equation and Bernoulli equation as the government equation, the0-1type BEM method is adopted to discrete the integral equation, an improved0-1BEM potential flow numerical model is established by combining the numerical sponge layer and the second reflection technology. In this model, the semi-mixed Eulerian-Lagrangian method (Semi-MEL) is employed to track the water surface, and the time integration is accomplished by the fourth-order Runge-Kutta method. The improved0-1BEM model is verified by simulating the propagation of regular waves and solitary wave over a submerged breakwater.Based on the VOF method, a turbulent flow numerical model is established by using the Reynolds time-averaged equation and k-ε equation. The numerical sponge layer is also utilized to eliminate wave reflection. Through the simulation of regular wave propagation, the stability and wave damping performance. The turbulence model is verified by some experiments.Secondly, considering the merits of both the0-1type BEM method and the VOF method, a new hybrid model (called0-1BEM+VOF model) by coupling with the0-1type BEM and the VOF method is developed. In the model, the intense wave motions at the proximity of the structures are calculated by the VOF method and the rest of the computational domain is modeled by the BEM. The velocities and free surface boundary conditions are presented in the transimmion domain, and the two-way synchronization solution process of the coupling model are carried out. In the transmission domain, the boundary velocity distribution, the free surface correction situation, the domain length and the distance from the position of the structure are studied, and then the recommended values of TD length and TD position are given. Bu using this coupling model, the wave transformation around a submerged breakwater, wave shoaling on a mind slope and wave impact on a horizontal plate problems are calculated. The numerical results have good agreements with the experimental results, and this shows that the presented coupling numerical model has wide applicability, good accuracy and efficiency.Finally, by using this coupling numerical model, a systematic study of wave overtopping on a sloping breakwater is carried out. In the study, the effect factors of crown height, platform width, wave steepness, relative water depth and slope on wave overtopping are analysed, the characteristic of the flow field and turbulence during wave overtopping process and the force analysis of the crown wall are discussed, and the calculation with the consideration of armour units is carried out. To consider the effect of the armour units, the equivalent friction coefficient μ*, which has been built link with the roughness coefficient KΔand can be converted from the roughness coefficient KΔ, is introduced into the governing equations. This idea is novel in the study of wave and structure interactions.