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A Passive Bio-inspired Micro-adaptive Separation Control Mechanism Derived from Shark Skin


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Flow separation has significant detrimental effect on vehicle performance and control, including increased pressure drag, vibratory loads, and destructive aeroelastic phenomena. The objective of this experimental work is to identify a bio-inspired passive mechanism for separation control functioning at the microscale level. This potentially transformative discovery has the ultimate aim to improve performance in numerous fluid dynamic applications (many of Army relevance) by finding inspiration from the skin of fast-swimming sharks(Figure 1). It is hypothesized that the movability of the shark scales results in a passive flow-actuated separation control mechanism functioning in the near-wall region of the boundary layer, whereby reversing flow near the wallin the presence of an adverse pressure gradient leads to scale actuation. This mechanism achieved by roughness elements (i.e. shark scales loosely sitting within a surface that are sensitive only to reversing flow) is hypothesized to act as a robust, unique, bio-inspired micro-adaptive flow control (MAFC) technology. Experimental research will be performed to understand the physics of the shark skin in controlling separation by: (1) Baseline experiments on the development of unsteady separation under laminar and turbulent boundary layer conditions; (2) Further testing of real shark skin specimens; (3) Using both 2-D and 3-D properly scaled rapid-prototyped models of shark skin,evaluate the effectiveness of a passive flow-actuated surface consisting of preferential flow direction elements,comparing with the baseline studies.



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