Aerodynamic Impacts of Wing Sweep on a Dual-Sided Coandă Actuator in Tailsitter UAV Design

The effectiveness of partial-span, dual-slot trailing-edge (TE) Coandă actuators on swept wings remains uncertain in the hover regime of rotor-blown wing tailsitter UAVs. This study investigates such effects using a benchtop setup with a vertically mounted wing in propeller driven flow. Force measurements were collected via an internal load cell across sweep angles ranging from 0° to 30°. For the unswept wing, dual-sided blowing—relative to single-sided blowing—improves linearity in the lift response, increases thrust vectoring effectiveness, and delays stall, albeit with increased mass flow demand depending on the chosen blowing strategy. Background-oriented Schlieren visualization reveals a correlation between stall onset and the Coandă jet turning angle exceeding 90°. As wing sweep increases, lift and pitching moment responses become increasingly asymmetric between dual-sided upward and downward blowing directions. This is attributed to lateral deviation of the propeller slipstream as the wing is swept, as confirmed by surface oil flow visualization. These results highlight complex propeller-wing actuator interactions in swept-wing tailsitter during hover and emphasize the need for tailored blowing strategies in future UAV designs employing TE Coandă actuation.