Study On The Nonlinear Hydrodynamics Of Two Dimensional Moving Bodies

The free surface flow generated by the moving bodies and the relevant hydrodynamic characteristic has been a hot research area in recent years.This thesis summarizes the existing relevant research for the two-dimensional submerged and floating bodies, and then investigates the free surface flow generated by a submerged circular cylinder in forward motion with horizontal constant speed, the problem of a sinusoidal oscillating circular cylinder at forward speed below and on the free surface as well as the twin-cylinders’ relative motion in infinite depth and shallow water by a two-dimensional fully-nonlinear time domain boundary element method based on potential theory. Results obtained by the fully-linear and fully-nonlinear simulation are respectively compared with existing analytical and numerical results and good agreement can be found. Convergence study with respect to both time step and element size has been undertaken and high accuracy can be achieved. The thesis mainly analyzes the existence of the fully-nonlinear steady solution for the two-dimensional circular cylinder in forward motion below the free surface at different constant speed and the oscillation characteristic around the critical frequency for a two-dimensional circular cylinder suffering sinusoidal oscillation while advancing with a constant speed.