Simulation-based Evaluation of a Cephalofoil-inspired Bow for Low Speed Passive Manoeuvrability of Torpedo-class Autonomous Underwater Vehicles

Torpedo shaped autonomous underwater vehicles (AUVs) displays poor hydrodynamic efficiency at low crusing speeds, resulting in endurance and mission effectiveness. This study investigated the integration of cephalofoil-inspired structures, which were modelled after hammerhead sharks (Smooth, Scalloped, and Winghead), onto the bow of torpedo-shaped AUVs. The design could improve low-speed manoeuvrability while maintaining hydrodynamic efficiency. Computational fluid dynamics (CFD) simulations were also conducted to replicate surge, pitch, and yaw manoeuvres at velocities ranging from ۰.۴ m/s to ۱.۲ m/s and yaw angles from ۵° to ۲۵°. The Smooth design utilising the NACA ۳۴۱۲ profile (۴۵۰ mm span length) then achieved a peak lift-to-drag ratio (CL/CD) of ۱۰.۰۳. In contrast, the Control design (torpedo hull without cephalofoil) attained a CL/CD ratio of ۱.۹۸. This finding demonstrated a fivefold enhancement in hydrodynamic efficiency for the Smooth design during surge manoeuvres. The Smooth design also attained CL/CD values between ۶.۳۹ and ۱۰.۶۸ during yaw manoeuvring conditions while producing the smallest turning radius of approximately ۰.۶۷ body lengths (BL). This outcome represented a nearly ۵۰% reduction compared to conventional torpedo hulls (~۱.۲ BL). Energy consumption analyses during the yaw manoeuvres further revealed that the Smooth design decreased power demands by ۸۰% and ۶۵% at ۰.۸ m/s against the Control and other cephalofoil designs, respectively. The pressure and velocity contour analyses then verified that delayed flow separation and stable vortex generation were the primary mechanisms facilitating these improvements. Overall, these cephalofoil-inspired bow integration effectively served as a low-complexity and passive manoeuvring strategy, enhancing agility and endurance for extended-duration ocean exploration and reconnaissance missions.

کلیدواژه ها:

Cephalofoil ، Torpedo autonomous underwater vehicles ، Yaw manoeuvre ، Turn radius ، Hammerhead sharks