The Calculation Of Large Amplitude Ship Roll Motion Based On The Nonlinear Time-Domain Panel Method

As one kind of large amplitude roll motion, parametric roll is an important stability failure mode in the second generation intact stability criteria, which are currently under development by International Maritime Organization (IMO). In this paper, the parametric roll is directly simulated using a coupled heave-roll-pitch model based on the three dimensional mixed source method. In this method, the Rankine sources are distributed in inner domain and transient Green functions are used in outer domain. By taking one passenger ship as an example, the calculation accuracy of common used approximate nonlinear method is compared with fully nonlinear time-domain method. The nonlinear Froude-Krylov forces and restoring forces are calculated by integrating wave pressure up to the wave surface in both methods, but the difference lies in the calculation of hydrodynamic forces: the hydrodynamic forces are calculated for the instantaneous hull surface in the fully nonlinear method, while the hydrodynamic forces only calculated for the average submerged hull in the approximate nonlinear method. The results show that the fully nonlinear time domain method is more accurate than the approximate nonlinear method in heading waves.