The Research On Trimaran's Longitudinal Motion Characteristics And Anti-pitching Appendixes

In recent years, with the development of modern shipping industry and technology upgrading, the SWATH, trimaran and other multi-hull ship as the representatives of the high performance ship have been paid more and more attention by the shipping industry and have been used as a variety of military demand. With better understanding of the ship, ship's performance has been improved. Because of the advantages of high speed, good sea-keeping,spacious deck and strong survival ability, trimaran has developed rapidly and has been widely concerned.Research shows that the sea-keeping of trimaran in waves is better than them of the same tonnage of conventional drainage mono-hull ship. but because of the characteristics of trimaran and its motion, the sea-keeping of trimaran in rough waves decreased. Therefore,how to improve the sea-keeping performance of trimaran is universal concern problem for people.Traditional displacement ships with SSB, fin, T foil and stern flap have been studied a lot,and have a better result. But the research of high-speed trimaran with appendixes is relatively less. In order to reduce the heave and pitch motion and improve the longitudinal motion performance of trimaran, this article study the effect of SSB, T foil and stern flap on the performance of trimaran longitudinal motion.In this paper, based on the theory of viscous flow and CFD technology, the methods of predicting the trimaran's movement in the regular head waves and hydrodynamic interaction between trimaran and appendixes are discussed. Using the method of discussion, the responses of heave, pitch, acceleration at the center of gravity and additional resistance are predicted. The characteristics of trimaran in waves are discussed. Then studying the effect of the trimaran installing SSB.SSB with fin, T-foil and T-foil with stern flap respectively on the longitudinal motion, through changing the shapes of SSB, dimensions of fins and installation positions of T-foil and lengths of stern flap. The optimization schemes of appendages are given.The study in the paper shows that in a wide range of low ?/ L the longitudinal motion performance of trimaran installed SSB, SSB with fin, T-foil and T-foil with stern flap is obviously improved, the responses of heave motion, pitch motion and vertical acceleration at the center of gravity decreased significantly. In high ?/L the installation of appendixes will make the longitudinal motion slightly increased. The installation of SSB, fin and T-foil will make the additional resistance in waves larger. The stern flat has no big effect on improving the longitudinal motion performance of trimaran, but it can reduce the additional resistance in waves and the effect on reducing resistance is obvious.