Numerical Analysis Of Interaction Between Waves And Perforated Caisson Breakwaters Based On SPH Method

After coming into the 21th century, more and more attention is given to the exploitation of marine resources, prevention and government of marine disasters have become more urgent, so the research of interaction between wave and ocean engineering structure seems to be particularly important. As the study of such hydraulic interaction problems is complexity, the methods of the previous experimental and theoretical analysis adopted not only consume much more time and higher cost, but also many details of the problems and physical phenomena cannot be rendered in-depth study duing to the influencing factors of model scale, simplifying assumptions and many other unforeseen cases. So an advanced computer simulation technology should be put forward to solving those complex research projects, and the application of the SPH approximation algorithm makes the problem more possible. No grid and adaptive characteristics of SPH method make it superior to the conventional FEM and DEM numerical methods which are based on grids. Therefore, the application of SPH approximation algorithm for the study of hydrodynamic problem is becoming a hot topic of current scientific research.Based on deeply understanding the SPH method, first and foremost in this paper, the issue for hydrodynamic will be described as discrete mathematic model; and Navier-Stokes equations of Hydrodynamic mathematical model which are solved by means of SPH approximation will be applied to study the interaction problems between wave and structure. During the study, The virtual particles which are impenetrable will be used to simulate the caisson border, a revised SPH method 2D numerical wave flume based on CSPM and Riemann solution is established here, and the wave pressure of particles boundary fixed on the caisson are amended for proposing a more stable flow field. In this paper, the SPH approximation algorithm is verified to be correct by the way of comparing the numerical results with linear wave theory values. By successfully the simulation of interaction experimental process between wave and perforated caisson, the relationship between the reflection coefficient Kr1 or the total horizontal force and their influencing factors are investigated, such as the wave dissipation chamber relative width B/L, the relative wave height H/L and so on; and a good agreement between the Krl and its influencing factors is made with the relationship equation based on the physical model experimental results, the wave pressure distributions of the inside or outside of the dissipation chamber are also given, and which will provide a new reference for design of the no roof perforated caisson, in this paper, the pressure and velocity field in or out of the wave dissipation chamber is analyzed here, as well as the complicated physical process of water particles flowing in or out of the dissipation chamber, especially, changes of velocity field in wave dissipation chamber is discussed in detail.Secondly, based on the revised SPH mathematical model, considering the affect of top cover gap on hydrodynamic performance of perforated caisson with a top cover. The experimental process of wave acting on perforated caisson with a top cover is also simulated. during the study, the relationship between the top cover relative gap s/H and the reflection coefficient is studied in depth, and it is concluded that the nonlinear relationship happens to the relative top cover gap s/H and the reflection coefficient, also the conclusion is verified by the experimental results and a good agreement is made, the influence of the top cover gap affecting on wave surface and pressure is discussed in the paper and the distribution of wave pressure along the height direction of perforated caisson is also given. At the same time, the impact of top cover gaps affecting on the horizontal force or its components are analysized here and a good agreement is made between numerical result and test data. The wave pressure and velocity field in or out of the wave dissipation chamber of perforated caisson under different top cover gap are investigated in detail, as well as the water particles velocity field changes in wave dissipation chamber of perforated caisson with a top cover.In the end of this paper, by connecting the SPH method with FEM calculation procedure, the SPH calculation result will be introduced into the finite element method program, and the transient dynamic response of the perforated caisson under wave action is studied. The accuracy of transient dynamic analysis method is verified by simulating the experiments interaction between the liquid tank and elastic plate. The dynamic stress changes of caisson under wave action are investigated in the paper and the dynamic stress distribution of the perforated caisson with a top cover are presented here, the effects of different top cover relative gaps s/L and dissipation chamber relative width B/L on dynamic stress of perforated caisson are analyzed and a conclusion is made that the dynamic stress will be nonlinear changes from the center of perforated plate to sides at the still water level. The method proposed in this paper can provides a new technical way for studying the stress response of perforated caisson under wave action.