Retard function and ship motions with forward speed in time-domain

The time-domain calculations of retard function and ship motions in waves by the direct time-domain method (DTM) and the frequency to time-domain transformation method (FTTM) are compared and analyzed. A Wigley-hull-form ship and an S60 ship moving in waves are examined, and the corresponding retard functions are in good agreement with those given by DTM and FTTM. The comparison of retard functions in different forward speeds by the two methods is observed, and the results of ship motions in forward speed are also compared with the experimental data. On this basis, the advantage and disadvantage of them are discussed.