Understanding of Drag Reduction & Biofouling using Shark Skin Denticle through CFD Simulation

Abstract

Nature has created ways of reducing drag in fluid flow, evident in the efficient movement of fish, dolphins and sharks. The skin of fast-swimming sharks protects against biofouling and reduces the drag experienced by sharks as they swim through water. The tiny scales covering the skin of fast-swimming sharks, known as dermal denticles (skin teeth), are shaped like small riblets and aligned in the direction of fluid flow. To understand the mechanism of shark-skin drag reduction, it is very important to understand the nature of fluid flow over an effective shark-skin surface. In thesis, to understand the drag reduction and biofouling property of sharklet type pattern, behaviour of fluid flow motion on three different patterns (plane, square and triangular) has been studied by computational fluid dynamics (CFD) simulation. A 3-D CFD model has been developed for the simulations. The contour of Pressure and Velocity is shown for a different inlet velocity. From the simulation results, it is found that in the case of sharklet type pattern lowest drag is occurred and it is mainly due to lesser contact area. Apart from this, antifouling in sharklet pattern occurs due to high wall shear stress at the tip of the surfaces. Due to high shear stress bacteria, can’t survive at the top surface and it results high antifouling property in sharklet type pattern. The drag force decreases approx. 26 percent in case of sharklet type pattern compared to plane surface. Distribution of local area averaged wall shear stress is observed for a different pattern and different velocity.