Longitudinal stability of planing boats with demihulls in high-speed navigation

Abstract

To study the influence of demihull layout on the longitudinal stability of planing boats in high-speed navigation, static water towing tests are performed on a monohull planing craft. The finite volume method combined with shear stress transport k-ω turbulence model is used to numerically simulate the flow field around the model using the overset grid technology. Comparisons of calculated and experimental values verify the effectiveness of the method. Then, the motion response and hydrodynamic characteristics of porpoizing trimaran with demihulls during high-speed navigation are calculated using a full factorial design spatial sampling and numerical method, and the influence of the longitudinal position and vertical depth of demihulls on the longitudinal stability of monohulls is analyzed. The results show that adding demihulls can delay the porpoising of planing crafts to a certain extent and improve the maximum speed. Moreover, the longitudinal stability of the planning boat can be improved by letting the demihull longitudinally approach the center of gravity or properly lean back and by increasing the immersion depth of the demihull. The longitudinal and vertical positions of the planing boat with good longitudinal stability are a=0.2L_m and c=30 mm, respectively, which provide a design reference for the demihull layout of planing boats at high speeds.