A potential flow model for linearized ship seakeeping in time domain is presented. The numerical algorithm is briefly sketched. The transient test technique, based on the interaction of a mathematical wave packet with the advancing ship, is numerically simulated and allow to recover the efficiency of frequency domain models. Solutions are presented for a frigate, a container-ship and a mathematical tri-hull. A set of experiments, also of transient type, have been performed to support the numerical findings.
"Practical" ship motion simulation tools have to be efficient enough to provide results in a relatively short time. On this ground, linearized frequency domain strip theories are largely employed because of the good compromise between simplicity, accuracy and computer requirements. On the other hand, the fully nonlinear three dimensional simulation in time domain is the natural avenue to deal with extreme wave conditions. For ship motions, the fully nonlinear approach is pioneered by the group led by R. Beck at University of Michigan through a desingularized Rankine panel method (see Scorpio et al. (1996)). The (weakly) nonlinear code SWAN2 developed at M.I.T. (see Sclavounos 1996) is the most extensively tested time domain code documented in literature. Here we present our attempt to develop a time domain algorithm for ship of arbitrary geometry and speed (Colagrossi and Landrini 1999). To recover the efficiency of two-dimensional (Salvesen et al. 1970) and three-dimensional (Bertram 1998) frequency domain methods we determine the ship behavior by studying the response to incoming wave packets (Ciauss and Vannahme 1999). Three categories of ships have been considered. The first one is representative of modern frigate ship: DDG 51. The second ship is a well known container vessel, S 175, for which experimental data are available both for head and following seas.
