Optimization Research On Longitudinal Seakeeping Performance Of Wave-piercing Catamaran

Wave-piercing catamaran is known as a high performance ship due to its high speed and excellent seakeeping performance. It's widely used in passenger ships and military fields. However, WPC have some shortcomings such as the excessive longitudinal motion. In order to ensure passenger's comfort, it is very necessary to further improve the longitudinal stability of wave-piercing catamaran in adverse sea conditions.In this paper, the equations of ship motion will be solved based on STF and the longitudinal motion of WPC in waves will be forecasted. Two ways of fixed hydrofoil and controlled hydrofoil are used to improve the seakeeping performance of WPC.In the anti-rolling research on fixed hydrofoil, we firstly analyzed the resistance and seakeeping performance of a T-foil fixed under the bow combined with three built-up appendages installed under the stern respectively which is stern interceptor, stern flap or tail fin. Then the state of multi-foil was designed based on the analytical results, and the stabilization effect was forecasted by the steady-wing theory and the revised lift formula of stern flap. Finally, ship model experiment was done to verify the effectiveness of multi-foil on the longitudinal stabilization. It was proved that the state of multi-foil reached the longitudinal anti-rolling design goals.Moreover, the automatic control T-foil and flap was studied on the basis of fixed hydrofoils. Considering the hydrofoil's motion characteristics, the linear vibration thin foil theory was applied and the hydrodynamic coefficients of automatic control T-foil was derived. The differences of motion forecast were also compared between the vibration wing theory and the steady wing theory. The optimal motion control of the flap on T-foil was determined by theoretical analysis, calculation and experiment. Finally the error between motion predictions and experimental values was analyzed. The results show that the vibration wing theory has better accuracy for predicting seakeeping performance. The automatic control T-foil system with appropriate control strategy has better anti-rolling effect than the fixed hydrofoil and it achieves the design target.