Time-domain Simulations Of Wave-current Interaction With Structures

Process of wave propagation is usually accompanied by currents. The coexistence of wave and current can influence the propagating property of respective holders. Synthesis of wave and current field is a complex combination rather than the simple piling up of individual character. In the present dissertation, a time-domain higher-order boundary element method (THOBEM) is developed to simulate wave-current interaction with 3D bodies.The emphasis is focused on the influence of the current on the results of hydrodynamic characteristics for wave-body interaction.Solving nonlinear problems by time-domain method, both the velocity potential and the wave run-up satisfy the nonlinear kinematic and dynamic boundary conditions at unknown instantaneous free surface. This results in update of free surface each time step, which increases the computing time tremendously. In this paper, a perturbation procedure is introduced to solve the problem of the wave-current-body interaction. The meshes are discreted on the initial position of the body responses and the mean free surface, which improves the computational efficiency of the time-domain method.In linear potential theory regime, the present model is carried out on the diffraction and radiation problems of wave-current interaction with 3D bodies. At first, a numerical study testifies validity of the model.The numerical results of wave-current interaction with circular cylinder are all in close agreement with the published results of the frequency-domain method, analytic method, and time-domain method. Then wave-current interaction with a fixed four-column platform is investigated, and the results agree well with experimental data. The above results give evidence to the accuracy of the numerical model of wave-current interaction with fixed bodies. Whereafter, the numerical model is extended to simulate wave-current interaction with floating bodies. The numerical results of wave-current interaction with a floating hemisphere match well with the published results of the frequency-domain method, which validates the accuracy of the numerical model of wave-current interaction with floating bodies. Furthermore, the interaction of wave-current with a three-legged bottom-supported platform is investigated. The emphasis is focused on the influence of the current on hydrodynamic characteristics for wave-body interaction. In the nonlinear simulation of mooring buoy interaction with wave-current, the mooring system is strongly nonlinear. The tightly stretched rope is chosen as research object in this paper. The numerical model is extended to simulate wave-current interaction with a mooring JIP Spar, where the effects of current on the cable forces, hydrodynamic forces on JIP Spar and body responses are system analyzed. Then, the numerical model is extended to the simulation of the freak wave-current interaction with mooring JIP Spar. As the main way to study of irregular wave expressed by spectrum of stochastic process, the Jonswap spectrum is chosen as research object in this paper. The hydrodynamic characteristics of freak waves,current interaction with structures are investigated.