Time domain non linear strip theory for ship motions

A new time-domain strip theory is developed in this thesis. Compared with traditional strip theory, the main difference is that the calculation is carried out in the time domain. Exciting forces and hydrodynamic coefficients are computed on the instantaneous wetted ship hull surface at each time step, which makes this new method possible to cope with relatively large-amplitude motions and non-constant forward speed problems. The basis of this new method lies in the strip theory of Salvesen, et al [56] and the early work of Westlake and Wilson [72]. The newly developed conformal mapping method enables the two-dimensional hydrodynamic coefficients of the sections with any type of shape to be computed accurately and efficiently. This new method is applied to calculate the hydrodynamic coefficients and motions of a Series 60 (CB = 0.7) ship model in regular waves. By comparing the results with experimental data and numerical results provided by other contemporary analytical techniques, important improvements are found within a certain range of wave frequencies. The numerical schemes are carefully verified and validated in a systematic manner to make sure that the current results are obtained.