Study on design of low Reynolds number reflexed airfoil for solar-powered UAV in flying wing configuration

Based on the application requirements of a small hand-launched solar-powered unmanned aerial vehicle (UAV) in flying wing configuration, the optimization design of the low Reynolds number (LRN) reflexed airfoil is carried out in this study to meet several requirements such as high lift, mild stall, demanding pitching moment. Firstly, the accuracy and reliability of both quasi-steady and unsteady numerical methods to simulate the LRN transition flow and the stall separated flow at large angles of attack (AOA) are validated by an airfoil case study at specified Reynolds numbers; Secondly, the LRN reflexed air-foil optimization design framework is established by using the CST parameterization method, the multi-island genetic algorithm (MIGA), and the kriging surrogate model; Lastly, the LRN reflexed airfoil optimization study is conducted by using the NACA 8-H-12 reflexed airfoil as the baseline airfoil, it shows that both the lift-to-drag performance and the stall characteristics of the designed airfoil is significantly improved when compared with the baseline airfoil, which are quite beneficial for the small hand-launched solar-powered UAV in flying wing configuration to realize the hand-launched take off and the high-lift long-endurance flight.