Aerodynamic investigation on propeller slipstream flows for solar powered airplanes

The aerodynamic characteristic on solar powered aircraft affected by propeller slipstream flows was investigated based on the structured/unstructured hybrid grid method. The effect of Propeller slipstreams was simulated with Multiple Reference Frames quasi steady method firstly in order to provide an initial flow field for the unsteady numerical simulation using sliding mesh methods. An experimental ducted propeller model belonging to NASA was used to verify the present methods and numerical results with a 5.3% error indicate a high level of agreement with experimental data; this demonstrates that the above methods have good accuracy to numerically simulate the aerodynamics of the solar powered aircraft at different propeller rotational speeds and angles of attack. According to the results, propeller slipstreams lead to notable lift and drag increments: the maximum lift increment and drag increment are respectively 26.7% and 34.7%. However, lift-to-drag ratio values for solar powered airplanes are reduced and the maximum decrement is 26.26%. The position where propeller slipstreams affect the chordwise pressure distribution mainly locates at the leading edge of the wing; this induces opposite pressure changes at the two sides of the propeller rotation shaft. However, the effect of the propeller slipstreams on the chordwise pressure distribution become little at the trailing edge of the wing.