Effects of outrigger configuration on trimaran stability in longitudinal waves

Abstract

A trimaran has excellent characteristics of transverse stability and less resistance because of its unconventional multiple slender hull form. However, the multi-hull configuration potentially triggers parametric roll due to the periodical fluctuation of metacentric height. In this study, an efficient numerical model was established to investigate the effects of the outriggers on trimaran stability in longitudinal waves, based on Froude-Krylov assumption and hydrostatic assumption. Then, the relationship between the metacentric height of the trimaran and the outrigger position was discussed, and the influence of heave/pitch motion responses on the wave stability of the trimaran was evaluated. Furthermore, a method of predicting the stability zone was proposed and checked by numerical simulation based on computational fluid dynamics. The relationship between the outrigger position and the potential risk of the parametric roll was analyzed by the obtained stability zones. It was found that the decrease in the outrigger displacement ratio and the increase in the clearance can significantly raise the risk of parametric roll of a trimaran.