Improving Seakeeping of Wave-Piercing Catamarans with Flaps Using PID Control

High-speed Wave-Piercing Catamarans play an important role in ocean transportation. Due to sharp vertical motion induced by the wave, seakeeping in heaving and pitching motions is invariably affected. To circumvent this problem, a flap, which is a flat plate employed as a hydrofoil to provide lift force in the water flow, is typically installed at the transom stern of each demihull. The strip theory is commonly employed for predicting seakeeping, but the accuracy of prediction is limited by the calculation of flap lift. In order to improve the accuracy of seakeeping prediction, the flaps are no longer considered as an isolated hydrofoil, but a part of the hull, taking into account the effects of transom stern, free water surface and cock-tail wake in this work. Furthermore, a PID controller is successfully designed to control the flaps. Simulation results demonstrate the effectiveness and efficiency of the proposed approach.