Time domain evaluation of ship motion with desingularized methodology

This paper presents an application of a panel method based in the time domain for the calculation of wave induced motions of a ship advancing in waves. The fluid domain boundaries are described using a grid of flat quadrilateral panels and the numerical solution is obtained by a desingularized approach in which, considering a desingularizing distance, a distribution of Rankine singularities has been applied upon the free-surface and inside the body. The method is aimed to deal with non linear effects even though in first applications body motions and wave amplitudes are assumed small and linear hypothesis has been exploited. The boundary conditions have been applied referring to the mean body wetted surface and to the calm water free surface. The solution is determined using an Eulerian time-stepping integration scheme in which the velocity potential computed at a given time-step allows to update the free surface boundary conditions to be imposed at the following time step. Once the current value of potential is obtained, the pressure on the mean hull surface can be calculated to evaluate the forces and moments acting on the body. The adequacy of the results has been verified applying the code to different typologies of hull and comparing the numerical output with experimental data freely available in literature. In this work, two ships have been chosen as test cases, the DTMB 5512 and the S175 hull. In addition, a comparison with other numerical methods has been carried out.