In this study, a high-speed planing trimaran hull form is designed, and the effects of different displacements and gravity longitudinal layouts on the performance of the trimaran planing hull in calm water are experimentally investigated in the towing tank of the China Special Vehicle Research Institute. Based on previous work, an innovative inner tunnel appendage hydroflap is mounted in the inner aft tunnel, located 1/8 L from the transom in the longitudinal direction with attack angles of 0° and 4°, respectively. Furthermore, a regular stern flap is mounted on the transom close to the chine. The towing test results show that, as the gravity center moves forward, the high-speed region resistance of the planing trimaran increases and the longitudinal stability is also strengthened. Further, the total resistance of the planing trimaran with a heavier displacement is larger while the average mass resistance declines; i.e., the resistance efficiency is improved. The results also indicate that the inner tunnel hydroflap and stern flap enhance the aft hull hydrodynamic lift and tunnel aerodynamic lift. As a result, mounting aft hull lift enhancement appendages can affect the bottom and inner tunnel pressure distribution and then cause a slight resistance decrease in the low-speed region. The value relationship of resistance between groups of appendages for the attached hull and bare hull is reversed at a speed of about Froude number 3.0. Although the aft hull lift enhancement appendages result in a higher resistance cost in the high-speed region, the longitudinal stability is effectively promoted and the occurrence speed of porpoising results in a delay of 1 to 2 m/s.

According to the requirement of high-performance development of modern ships, it is necessary to quickly and accurately predict the maneuverability of ships under wave conditions. In this paper, based on the CFD (Computational Fluid Dynamics) method in the commercial software STAR-CCM+, the numerical simulation of roll decay motion, pure heel motion, pure heave motion, and pure pitch motion of ship model 5415 is carried out. The relevant hydrodynamic derivatives are obtained, and the results are in good agreement with the experimental values. The equations of motion related to the heave and pitch motions are established according to the MMG (Maneuvering Motion Equation Research Group) model. Then, based on the above dynamic equations, the wave force module is added to successfully simulate and predict the pitch and heave responses of the ship under regular wave conditions, and it is concluded that the simulation model for rapid prediction is also applicable under waves.