Vol 77 No 4 77414

Abstract

Numerical studies on parametric roll have mainly focused on head and following seas, whereas parametric roll in oblique head seas remains less fully understood due to the coupled effects of roll, sway, yaw, and the propulsion-steering system. In this study, a CFD-based numerical framework is developed for predicting parametric roll of a self-propelled KCS ship in oblique head seas, considering the coupled interactions among the hull, rudder, and propeller. The effects of model speed and wave heading on parametric-roll responses are investigated, and two mitigation strategies are examined, namely passive roll reduction using a bilge keel and active avoidance through speed control. The results show that parametric roll in oblique head seas is highly sensitive to model speed and wave heading. The roll response becomes pronounced when the encounter condition falls within the parametric-roll-sensitive range, whereas it is significantly weakened when the ship moves away from this range. Wave headings closer to head seas correspond to a more critical parametric-roll region. The bilge keel suppresses roll growth by increasing roll damping and reducing the roll moment, while speed control mitigates the nonlinear response by adjusting the encounter frequency. The present study demonstrates that CFD can be used not only to identify parametric-roll occurrence, but also to support the development of passive mitigation and active operational guidance for self-propelled ships in oblique head seas.