Control of Flow Separation on 3D Printed Shark Skin as a Function of Boundary Layer Thickness

“Nature knows best” is an age-old maxim that has helped mankind innovate throughout history. Aquatic creatures can provide valuable knowledge to better the efficiency of vehicles from a fluid mechanics perspective. Previous studies have found that the fastest shark in the world, the mako shark, has passively actuating scales which bristle up to 50 degrees, to inhibit flow reversal near the surface to control flow separation and thus reduce pressure drag. Through testing in a water tunnel, 3D printed models of actuatable shark scales have proven the ability of these scales to delay separation of the boundary layer in laminar and turbulent flow upon encountering an adverse pressure gradient (APG) created by a rotating cylinder. New experiments were conducted using DPIV to test the importance of the ratio of boundary layer thickness to actuation height for turbulent boundary layer conditions. It was found that a larger boundary layer thickness provided the best ability of the scales to perform. Experimentation to find how these manufactured scales work optimally was an appropriate step in furthering an understanding of this bio-inspired mechanism.