Numerical evaluation of pentramaran hullform for roll resonance

Roll resonance is a condition in which an otherwise stable ship displays unstable roll motions. This phenomenon for monohull vessels is well known to marine industry since long and is now being formally incorporated in the Second-Generation Intact Stability criteria (SGISc) by IMO. Trimaran hullform has also received attention by the researchers and has shown potential to experience roll resonance. Pentamaran hullform have been conceived to reduce resistance of the outriggers by introducing shorter aft side hulls and "flying" forward side hulls. It raised the question about roll resonance characteristics of the novel hullform. This study presents a numerical technique based on the well-established analytical methods available for monohull to identify likelihood of roll resonance in pentamaran hullform. In this work 33 configurations of a pentamaran hullform have been studied to identify the impact of relative positioning of outriggers on the onset of roll resonance. A modified Mathieu equation has been proposed for the numerical evaluation of pentamaran hullform roll resonance. Numerical simulation suggest that pentamaran hullform may suffer roll resonance under certain configurations of side hulls.