Investigation of Separation Control in a Turbulent Boundary Layer Using Passive 3D-Printed Shark Denticles

Separated turbulent boundary layers are an engineering problem due to their drag-inducing properties. A possible solution may lie with the shortfin mako shark whose scales’ flow-activated bristling under reversing flow conditions may passively control separated flow. An adverse pressure gradient is induced through a rotating cylinder to produce the backflow near the wall over the 3D printed array of shark scales. This passive bristling has been observed by biologists to be caused by reversing flow on real shark skin samples. Controlling effects of these scales have been seen within a 2-D separating turbulent boundary layer from previous researchers. Several shark-inspired 3D-printed models have been constructed to analyze flow control capabilities of man-man models. Data acquisition is conducted using DPIV in a water tunnel to document flow control capability, and investigate the range of permissible actuating height needed to implement flow control. Re ranging up to 8.8x10^5 in the boundary layer were tested, to vary both the boundary layer thickness and reversing flow speeds over the 3D printed models. Results are compared also to a smooth flat plate to discern the amount of separation control for a given flow regime.