| A numerical wave tank(NWT)based on potential theory has been built using the Fast Multipole Boundary Element Method(FMBEM).Runge-Kutta 4th-order(RK4)is also used as a time marching tool to precisely obtain the velocity potential and wave elevation at each time step,while the acceleration potential which is applied to calculating the body motions and hydrodynamic forces simultaneously will be solved by mode decomposition method or the indirect method.Linear irregular wave propagation has been realized in this NWT,by which the high rapidity and precision of FMBEM-based NWT could be validated.In addition,the interactions between irregular wave and freely floating body or undulating bottom are investigated,and the comparisons between irregular and regular wave results demonstrate the great importance of studying random wave cases.Moreover,a nonlinear wave refactoring method is proposed in this thesis.Due to the use of nonlinear dispersion relation,iterative adaption of wave amplitude and wavelength,internal division and region overlapping technique,the present method not only can separate the higher harmonic components of strong nonlinear wave well,but can also spatially and temporally detect the fluctuation of wave parameters.The high performance of present method is validated by artificial test data,and the simulated results from FMBEM-based NWT are also investigated.With the help of present separation method,the temporal and spatial variation of wavelength and wave amplitude of numerical results could be displayed and analyzed,and the in-depth mechanics of bottom effect on traveling waves could be understood better. |
PDF Full Text Request