Experimental and Numerical Investigations on the Effect of Bio-Inspired Covert Flaps on High Lift Low Reynolds Number Airfoils

The military and commercial sectors use unmanned aerial vehicles (UAVs). In the military, UAVs are mostly used for strategic goals and for reconnaissance. For a long time, there has been active study into the incorporation of bio-inspired techniques to improve the performance of air vehicles. UAVs can be equipped with several gadgets, such as hidden flaps. Covert flaps, also known as covert feathers, are aeroelastic devices used by birds as a natural flow separation control mechanism for reducing or managing flow separation, delaying stall as well as enhancing lift. To aid in maneuvers and stability, it can be used to enhance or decrease the aircraft lift and drag. In this study, the effects of a flap inspired by a clandestine operation on SELIG1223 are demonstrated experimentally. First, by altering the configuration of flap specified by length, attachment position, and deployment angle, the key factors that enable a flap positioned on an airfoil at a high angle of attack to generate higher lift and enhanced aerodynamic efficiency are identified. Two different forms of flaps—freely deployable flap and a stationary flap—are studied in terms of lift and drag. The configuration with 80% chord location and deployed at an angle of 15° with the surface shows better characteristics with an increase in lift by 21% at the post-stall angle of attack and delays the stall by 5°.