ABSTRACT
A reliable prediction of the ship behavior, in actual weather condition, is currently one of the major issues for ship researchers and ship industries as well. Most of the ship design approaches are based on calm water assumption, although marine vessels are going to operate in seaways. In particular it is well known that ship dynamics in irregular waves can lead to unexpected large amplitude motions (IMO 2007) with critical consequences for cargo and passengers. The need of further investigations on ship behavior and ship accelerations in heavy sea states is pointed out (France et al. 2003). Several ship research fields are nowadays focusing on the effects of irregular sea states on ship design and operations (Belenky et al. 2011) (Journée & Massie 2001); however ship maneuvering performances are still predicted on calm water assumptions (Abs 2006). Since the ship always sails in waves, the maneuvering performance in a seaway condition may be significantly different from that in a calm water condition. While the ship is steering in waves, wave-induced motion and drift force increase; thus, large accelerations can arise due to the combinations of different motions.
