Interceptor Effect on Lift and Drag in High Speed Planing Hull

Abstract In this paper an attempt has been made to study the effectiveness of interceptor on lift and drag as this device is nowadays used by both partial and dynamic lift crafts. There is change in pressure distribution at the stern region where interceptor is fitted which helps in the lift of vessel. This study focuses on the effect of interceptor in high speed planing hull with 20deg deadrise angle based on experimental, numerical and empirical approaches. Experiments were conducted in the Towing Tank facility, Department of Ocean Engineering at IIT Madras and numerical simulations were carried out in still water condition for the cases of the hull with and without interceptor. Results showed good reduction in resistance and trim of the vessel when fitted with interceptor in planing regime. Savitsky empirical relations for bare hull and Steen empirical equations for hull with interceptor are used to estimate lift and drag on the vessel. The results of this study show that interceptor creates more lift on the vessel due to the pressure created at the stern region which helps in drag reduction and further in better control of trim on the vessel. Measurements were also made to confirm that interceptor has an effect on the dynamic lift of the hull and hence a change in resistance resulting in control of the trim angle.