Hydrodynamic Behavior Numerical Simulation Of Underwater Excitation Object For Desingular Source Panel Method

In this thesis,the numerical simulation method of 2D and 3D submerged and excited body are presented.Based on the source panel method,the mathematical equation of submerged and excited cylinder model in a 2D time domain and the submersed single and excited sphere and double and excited sphere model in a 3D time domain are established,the hydrodynamic behavior of the immersed and excited structure are studied.The main works of this paper are as follows:(1)Based on the source panel method,the mathematical model of underwater cylinder which is inclined excitation are established,the boundary integral equation is established by arranging appropriate source points on the free surface and cylindrical surface,and reduces boundary integral equations into linear algebraic equations,numerical simulation of hydrodynamic characteristics of surface pressure and wave height of submerged cylinder under inclined excitation.The numerical results show that the surface pressure and free surface wave elevation are accompanied with the excited frequency,amplitude and submerged depth.The free surface wave presents linear evolution when small amplitude appears excitation.When the submerged depth of the cylinder decreases,the large amplitude of the free surface wave increases obviously.The larger submerged depth of the cylinder and the smaller amplitude of the free surface wave elevation.The pressure on the upper and lower surfaces of the cylinder appears with a periodical variation.(2)Rankine sources are distributed in an appropriate surface in the sphere.The third-order Adams iteration is established on the free surface and non-singular Rankine source panel method is established in the inner region.The free surface wave elevation,velocity potential and the hydrodynamics variation of the submerged sphere are simulated numerically using a 3D singular source Green's equation.The numerical results show that the farther the free surface sources away from the sphere,the less the influence of the sphere excitation on the wave elevation is.Under the vertical excitation of the submerged sphere,the wave elevation of the free surface increases first and then tends to be stable with time.The resistance on the sphere fluctuates regularly with time and the pressure on the surface of the sphere changes periodically.Compared with the upper surface area,the pressure in the lower surface area has a larger peak value and decreases rapidly.The additional mass depends on the excitation frequency and the effect of the submerged depth on the damping coefficient is negligible.(3)The desingular source distribution method of submerged double sphere in a3 D domain is established and the evolution of wave elevation is studied on free surface under the resonant double sphere.In this paper,the numerical simulation of the free surface wave can be presented with different times and different excitation frequencies.The numerical simulation results show that the evolutive process is detail depicted with the wave profiles under the double resonant spherical excitation.The numerical results show that the free surface wave elevations depict the phenomenon of periodic beating under the single vertical resonant excitation,and the number of periodic beating is different with the different excited frequencies.