Aeropropulsive Performance Modeling of Over-the-Wing Propulsion at Incidence

Abstract

A semi-analytical model is proposed that incorporates aerodynamic interactions between the rotor- and wing-induced flowfields. Predictions are validated through experiments performed with an array of five rotors above an airfoil, where the angle of attack, advance ratio, and chordwise rotor position are varied. At moderate angles of attack, the propulsive thrust is reduced due to the acceleration induced by the wing’s circulation. Around the stall angle of the isolated wing, the rotors re-energize the boundary layer when operated in low-thrust conditions. By increasing the thrust, a pronounced region of reverse flow between the rotors and wing adversely affects the leading-edge separation delay over the wing that occurs for lower thrust settings. However, in this condition, the wing–rotor-array system exhibits increased thrust compared to the attached flow condition due to the rotors ingesting low-momentum flow. In addition, the rotor-induced flow over the wing augments suction, while the pressure side is subjected to a pressure increase, ascribed to flow entrainment from the rotors. After comparison with the experimental observations, it is confirmed that the model predictions accurately describe the lift and thrust performance trends, aside from a discrepancy in the lift force when the rotors are operated in low-thrust conditions.