Circulation-controlled high-lift wing for small unmanned aerial vehicle

Small unmanned aerial vehicles (SUAVs) have recently attracted considerable research and development interest owing to their small size, portability, and limited operational risk. In SUAVs, the Reynolds number Re is typically very low because they are small and fly at low speeds. The Reynolds number strongly influences the airfoil performance, and at Re = 105, the lift-drag (L/D) ratio decreases significantly and the airfoil performance deteriorates. Since SUAVs must be able to carry payloads such as communication devices and observation equipment, the challenge is to maintain sufficient payload capacity. We propose a high-lift wing that can maintain a high L/D ratio and increase more payload in the low Reynolds number region (Re = ~105) by small size airfoil (SUAV), thereby expanding the application range of SUAVs. A high L/D ratio is achieved by converting the top and bottom face of the wing into a driven belt, thereby actively adding momentum to the flow around the wing. A test was conducted at a Reynolds number of 1.1 × 105 chord. The maximum L/D ratio increased by a factor of 1.67. A flow visualization test was also conducted at a Reynolds number of 105. Flow attachment was observed up to an angle of attack of 28° with the device; in comparison, the flow separated at an angle of attack of 11° in a non-driven wing.