CFD prediction of ship seakeeping behavior in bi-directional cross wave compared with in uni-directional regular wave

Abstract

The seakeeping behavior of a vessel in multi-directional wave differs significantly from that in uni-directional wave. Given that a vessel operates in multi-directional or short-crested waves during its whole service period, it is important to have a better understanding of the influence of wave directionality on ship seakeeping performance. In this study, CFD method is used to simulate ship motions in both uni- and bi-directional regular waves. A S175 hull model is adopted for seakeeping analysis. Both uni- and bi-directional waves are generated by velocity boundary method. Overset grid technique is adopted to simulate ship motions in waves. Ship motions in different uni-directional regular wave conditions are predicted and validated by experimental data at first. Then ship motions in monochromatic bi-directional wave conditions with different control parameters such as wave length, ship speed and ship heading angle are predicted and analyzed. The comparative results indicate that ship motion response in bi-directional waves is generally larger than that in uni-directional waves. Moreover, severe bow slamming and green water under bi-directional waves are also observed and investigated. This study indicates that ship seakeeping behavior in bi-directional wave should be paid enough attention during ship design and evaluation.