Post-Stall Performance Improvement through Bio-inspired Passive Covert Feathers

Document Type

Conference Paper

Publication Date


Publication Source

54th AIAA Aerospace Sciences Meeting


Inspired by birds' covert feathers, previous research has shown that artificial self-deployable flaps placed on the suction surface of wings can act as a passive boundary layer flow control mechanism improving post-stall wing lift performance by as much as 15%. Parametric variations are performed in this study, to investigate the range of effectiveness of these artificial flaps. Experiments were performed at the University of Dayton Low Speed Wind Tunnel at a Reynolds number of 2.0x105. A NACA-0012, an intermediate camber USA-28 and a highly cambered Eppler-423 were studied.

Flap settings (flap length and chordwise placement) informed by previous research by the authors at another facility did not result in similar improvement in the present study. Subsequent experiments and complementary XFoil investigations revealed that each wing will respond differently to the placement of the artificial feathers depending on the wing's stall characteristics, boundary layer thickness, and pressure distribution. No universally effective flap configuration was discovered, however, an optimum flap configuration was ascertained for each wing resulting in post-stall lift performance improvements on the order of 5% to 30%. This was true even for the NACA 0012 which experienced a leading edge stall at the Reynolds number tested. Segmenting the flap in the spanwise direction was found to be beneficial in the case of trailing edge stall. Finally, some insight into the physics underlying the effectiveness of these flaps can be gained through careful evaluation of the pressure gradients along the upper surface. This insight can ultimately inform optimal flap placement.




Permission documentation is on file.


American Institute of Aeronautics and Astronautics

Place of Publication

San Diego, CA