Study On Wave Impact On Horizontal Plate Based On SPH Method

With the exploitation of marine resources, the safety of coastal and offshore engineering structures, espcially wave impact on the strucures, has become the focus. In the process of wave slamming, the impact pressures with short duration and high peaks occurs when the waves hit the subface of the structure, which causes the destabilization of superstructure and the fratigue failure of joints. Hence, it is of great scientific value and pratical significance to do the research on the characteristics of flow field and pressures in the process of irregular wave impact.This dissertation, in terms of Smoothed Particle Hydrodynamics (SPH), presents the experimental investigation and numerical simulation of the slamming on the horizontal plate suspended over the water surface in the splash zone. It analyzes various factors that infuence the wave impact on horizontal plate and the intaneous velocity field of wave slamming.Firstly, SPH method is applied to the study of the interaction between waves and structures in this dissertation. It elaborates on the theory of SPH method and the process of numerical simulation. SPH method is improved by iterative soluting of Poisson equation for pressures field, and meanwhile introduces sub-grid turbulence model into the equation so as to more accurately describe the turbulence characteristics at the time of wave breaking and the pressures generated by the high-speed wave impact in this paper. Profound research is also made on boundary conditions. Through comparative study of five different solid boundary treatment methods, the advanteges and disadvantages of each method are analyzed. Besides, virtual particle method is improved with the introduction of mirror image theory. Meanwhile, a new solid boundary treatment method (solid boundary particle method) is provided, whose validity and precision is proved by means of experiments. Thus, the accuracy and computational efficiency of the pressures on the boundary is improved.Secondly, a numerical wave tank model is built on the basis of SPH method. A numerical simulation is implemented on solitary wave breaking on beaches and solitary wave ascending on the wall. Through the comparative analysis between the experiment and the results, it can be seen that the wave peak is at rather high speed, leading to the vertical shape of wave surface. The wave peak rushes in the form of a tongue until it falls into the water body below and a large number of bubbles are wrapped. Then wave splashes once again, presenting clear characteristics of wave breaking in form of a roller. Through the detailed analysis of the flow field and the impact pressures, we have a better understanding of the wave impact mechanism. At the same time, wave height rise of shallow-water waves is succesfully observed through the numerical simulation on cnoidal wave breaking on beaches.Thirdly, the two-dimensional numerical model of solitary wave and regular wave slamming to leveling board is built on the basis of SPH method. A systematic study is made on regular wave impact pressures on the two-dimensional horizontal deck, through which the distribution of wave impact pressures on the subface of the structure is achieved for different wave height, period and relative clearance and the relation between the impact pressures and wave height, period and relative clearance is analyzed. Through the comparison between the results of numerical and experimental data, we have a better understanding of the magnitude and the distribution rule of the regular wave impact pressures on the two-dimensional horizontal deck.Lastly, the three-dimensional experiment study is made on regular wave impact on horizontal plate. The distribution of wave impact pressures on three-dimensional structures is achieved for different wave height, period and relative clearance. The relation between the impact pressures and wave height, period and relative clearance is analyzed. Meanwhile, the three-dimensional numerical model is built on the basis of SPH method. An initial numerical simulation is performed on the interaction between regular wave and three-dimensional horizontal plate.