Mitigating load responses of high-speed catamarans via ride control systems: An experimental study in irregular waves, part2: Slamming kinematics and energy transfer

• Towing tank experiments on a 2.5 m catamaran with an active ride control system investigated slamming in irregular waves. • Slams occurred when relative bow immersion stayed below the maximum centre-bow archway height. • Greater bow immersion increased the likelihood of severe slamming events. • Slam magnitude showed weak correlation with maximum and relative bow velocities. • Nonlinear pitch control algorithm reduced overall slam-induced strain energy by 96% in moderate waves. This study investigates the influence of a Ride Control System (RCS) with stern-mounted trim tabs and a bow-fitted T-Foil on slam kinematics and energy transfer during slamming, using a 2.5 m scale model of a 112 m Incat Tasmania high-speed catamaran in irregular waves. Towing tank tests were conducted at a forward speed of 2.89 m/s (37 knots at full-scale) in irregular head seas with significant wave heights of 60 mm and 90 mm, corresponding to 2.7 m and 4 m at full-scale, respectively. It was demonstrated that relative bow immersion is the kinematic parameter most strongly correlated with slam severity and is associated with a higher likelihood of severe slamming. In contrast, slam magnitude (quantified as peak integrated centre bow force derived from strain measurements) showed no strong correlation with either the relative bow velocity at the instant of slamming or the maximum pre-slam relative bow velocity. While these velocity factors showed weaker correlation with slam magnitude reduction compared to relative bow immersion, their importance increases when evaluating the effectiveness of control algorithms that similarly reduce relative bow immersion. The nonlinear pitch control algorithm was found to be the most effective in reducing relative bow immersion, reducing it by 17% and 21% in 60 mm and 90 mm wave heights, respectively, compared to the No RCS condition. Strain energy analysis revealed that this control algorithm reduced overall slam-induced strain energy of the model by 96% in 60 mm waves and 68% in 90 mm waves over a 54-second model test period compared to the No RCS mode. Furthermore, this algorithm mitigated the maximum peak strain energy in the centre bow by 70% in 60 mm waves and 47% in 90 mm waves, highlighting its potential to reduce slam-induced loads and improve the structural design of high-speed catamarans operating in challenging sea conditions.