Aerodynamics and Flowfield of Distributed Electric Propulsion Tiltwing During Transition With Deflected Trailing-Edge Flap

Abstract

The aerodynamics and flowfield of a rectangular semiwing equipped with four four-bladed propellers and a 40%-chord full-span plain trailing-edge flap were investigated by using force balance and particle image velocimetry (PIV). The distributed electric propulsion (DEP) wing was tilted from zero to 90-deg angle of attack. The maximum lift coefficient, lift-curve slope, and stall angle of the DEP wing were found to increase significantly with increasing propeller rotation. The DEP wing also exhibited a gradual stall in contrast to the sudden stall of the baseline wing. The lift coefficient of the DEP wing positioned vertically at 90 deg was also found to be greatly increased with increasing propeller rotation. Regardless of the magnitude of propeller rotation, the general pattern and behavior of the lift curve were consistent. The deployment of the flap led to a further increase in the maximum lift coefficient and lift-curve slope but an earlier stall and an increased drag of the DEP wing as compared to the unflapped wing. The flap deflection also led to a lowered lift coefficient in the poststall angle-of-attack regime as compared to the unflapped DEP wing. Gurney flap was also employed to further increase the lift generation of the DEP wing. The lift augmentation produced by the propeller slipstream was supplemented by the PIV flowfield measurements.