Study on the Porpoising Phenomenon of High-Speed Trimaran Planing Craft

This paper presents the application of Computational Fluid Dynamics (CFD) simulations to the heaving and rolling motion of the planing craft under different speeds and centers of gravity. Comparing the flow lines, the pressure distribution at the bottom of the boat, the heave and the trim angle before instability with those elements after instability, a critical trim angle results in the early separation of the air in the bow. Meanwhile, due to effect of aerodynamic lift, the bow is lifted, which eventually leads to instability of the hull. Forward or upward movement of the center of gravity may eliminate or postpone the porpoising, the backward center of gravity may result in the unstablity of the ship. Serious porpoising is random and irregular. It will damage the structure of the hull, affect the maneuverability of the ship and threaten the safety of the crew.