Numerical Simulation Of Interaction Of Three-dimensional Internal Solitary Waves With The Structure In A Stratified Flow

With the progress of oceanographic studies and ocean resource exploitation, more andmore attention are paid to the complex dynamics of the ocean internal wave. The internalsolitary wave (ISW), a special kind of nonlinear ocean internal wave, which is of highfrequency, large amplitude and short cycle, spreads unidirectionally. What’s more, the speedand the waveform of ISW stay almost the same throughout its propagation. Therefore, ISW,with its huge energy and the extremely strong current it causes, is one of the major threats tothe existence and proper working condition of submerged bodies, drilling platforms,submarine pipelines and other offshore structures. It is not only academically important, butalso of pratical significance for simulating such a problem in the stratified ocean.This thesis is an attempt to study the interaction between ISW and submerged bodieswith the CFD numerical simulation approach. First, the thesis begins with a systemic reviewof studies on ISW home and abroad, and introduces briefly the computational fluid dynamicsand the theory and methodology of numerical wave tank. Second, with KdV theory as theframework and based on Navier-Stokes equations, a numerical3D ISW flume in a two-layerflow system is developed to simulate the generation and absorption of ISW. Other techniquesapplied are volume of fluid (VOF) interface tracking, setting boundary wave generation andnumerical dissipation wave absorption. Then the interaction between ISW and the submergedbodies is simulated in the numerical3D ISW tank.The novel points and main conclusions of this thesis are described as flows.(1)By means of the method of setting boundary wave generation and numericaldissipation wave absorption, a numerical3D ISW flume in a two-layer flow system isdeveloped to simulate the generation and absorption of ISW and analyze its structuraldistribution in the flow.(2)With the effectiveness of the interaction between ISW and the submerged bodies issimulated in the numerical3d ISW tank to analyze the different loads on the submergedbodies at various depth. As shown by the results, the load becomes the heaviest when thesubmerged bodies is passing through (in the peak of) the surface of the ISW.(3)From the results, the ISW simulations in3D model and2D model are compared toverify the advantages of the former, but2D model are simplified restrictions and lack ofrationality. And to pave the way to more complex hydrodynamic coupling problem in thefuture. As shown by the study, the CFD numerical approach to simulate the interaction between3D ISW and submerged bodies produces better results. And the approach, effective and moredirectly, would provide important applications in continental shelf resource exploitations andmilitary activites.