Kirigami metasurfaces provide the opportunity for deployable surface modifications that can potentially be used for aerodynamic flow control. An exploratory experimental investigation was performed to assess the flow control capabilities of a triangular and circular kirigami device on an airfoil in an open-jet wind tunnel. 
A finite element model of the kirigami was validated against laser scans of a vinyl-cut prototype, showing strong agreement in deployment height and successfully highlighting non-uniformity effects. Using rounded rectangular cut-outs on the strip outside the kirigami geometry, both the deployment height and the deployment uniformity were increased. The device was placed between x/c = 0.55 to 0.7 on a DU96 airfoil, with a device height ranging h/δ = 0.1 - 0.3. 
PIV measurements showed that at 6–10° angle of attack, separation was aggravated, whereas at 12–14° separation was reduced, with smaller separation regions, weaker reverse flow, and significant drag reduction. At higher angles, the kirigami became submerged in the separation bubble (h/δ = 0.05) and lost effectiveness. Results indicate that the device does not act as a vortex generator. Instead, it is hypothesised that either the kirigami modifies near-surface flow through blockage, causes a reduction of shear stress on the kirigami device, or disrupts backflow structures that drive flow reversal. ... Read more