Experimental Study of Rigidity Effects of Shark Skin Denticle Models on a Turbulent Separation Control

Bio-inspired flow control mechanisms have allowed engineers to learn from nature. One of these animals is the mako shark, whose scales bristle when met with reversing flow; this may be linked to a passive flow-actuated separation control mechanism. A study of how the rigidity of these shark scales can affect the separation control mechanism is of interest to better understand the limitations and better design bio-inspired surfaces for separation control. Using a rotating cylinder, an adverse pressure gradient is induced creating a separated region over several different bio-inspired models resembling fixed shark scales at different angles. In this experiment, the boundary layer grows to sizes large enough that the scale of the flow is increased, making it more measurable to DPIV. Additionally, the large boundary layer allows for models to be sized to fit within the bottom 5-10% of the boundary layer. Plates with model shark scales fixed at 0, 15, 30, and 45 degrees are investigated at a Re in the range of 5 x 10e5. This data is compared to a smooth flat plate as well as that obtained for passively bristling scales, free to move within the flow to verify how the rigidity of the scales interacts with reversing a flow region.