On the Hydrodynamic Effects of the Eidonomy of the Hammerhead Shark’s Cephalofoil in the Eye Bulb Region: Winglet-Like Behaviour

Abstract

External morphology (eidonomy) of marine creatures, developed by the evolution process over the course of millions of years, plays a crucial role in their locomotion and swimming performance. In this paper, hydrodynamic impacts of the cephalofoil tip eidonomy (tip bump) in the eye bulb region of a scalloped hammerhead shark, Sphyrna lewini, are studied with the aid of computational fluid dynamics (CFD). In this regard, two separate geometries are designed here; one corresponding to the real geometry of the hammerhead shark’s cephalofoil with a tip bump (eye bulb region) and another one, a modified version with a flat tip without the aforementioned bump. Turbulent flows encountered in the problem are simulated using the Lam-Bremhorst turbulence model at different angles of attack (AoA) and a sideslip angle, at high Reynolds number, 106, corresponding to the swimming of a juvenile hammerhead shark with a speed of 1 m/s. The results show that the strength (circulation) of the wing tip vortices reduces by the external geometry of the hammerhead’s cephalofoil tip; in this sense, ‘cephalofoil tip’ with its unique morphology behaves as a winglet.