Aerodynamic design of low-Reynolds-number wing taking into account the multiple propellers induced effects

Based on a certain hand-throw solar-powered unmanned aerial vehicle (UAV), the optimization design approaches for low-Reynolds-number wing coupled with multiple propellers induced effects are studied. The corresponding quasi-steady procedure based on the vortex lattice method (VLM) of lifting line theory and the low Reynolds correction (LRC) method based on the reference airfoil aerodynamic properties database are developed to simulate the multiple propellers/wing aerodynamic interference at low Reynolds numbers. The reliability and accuracy of the simplified numerical method (VLM procedure and LRC method) are testified with several cases studies and their comparison with experimental results. Both the direct optimization design and inverse design of the simplified hand-throw solar-powered UAV model in tractor configuration are conducted, and the optimization results are examined with high-accuracy CFD technique. It shows that (a) the low-Reynolds-number flow can be simulated by the VLM-LRC method efficiently and accurately; (b) the aerodynamic properties of the optimal wing cannot be improved when the propeller slipstream effect is not taken into consideration in the conventional design approach; (c) the wing drag performance can be greatly improved with the optimization approach that takes into account the multiple propeller slipstream effects, and the optimized wing has a drag reduction of 19.52 counts at the design state.