Aerodynamic Interaction Effects Between a Propeller Slipstream and Single Slotted Flap

Abstract

A 3D unsteady RANS simulation utilizing the Spalart-Allmaras (SA) turbulence model was conducted to investigate aerodynamic interactions within a propeller-wing-flap system. The research specifically examines the complex flow field around a slotted flap, highlighting the interaction between the propeller slipstream and the main wing and flap during powered high-lift conditions. Operating conditions include a chord-based Reynolds number of 2 million, with thrust and flap settings reflecting take-off conditions (propeller advance ration of 0.765, thrust coefficient of 1.267, flap deflection angle of 15 deg) at an angle of attack of 8.3 deg. Chordwise pressure distributions and surface shear stress contours show strong agreement with previous experimental measurements and oil flow visualizations of the same geometry. Findings indicate that a portion of the propeller slipstream transfers from the pressure side of the main wing to the upper side of the flap through the cove, dominating the flap flow field. Although the upper side of the main wing experiences fluctuating flow originating from the propeller slipstream, this flow does not induce unsteadiness or penetrate the flap upper side boundary layer along the wing span. Furthermore, it is shown that the shedding of vortices from the propeller root, along with the resulting vortices on the lower side of the geometry, weakens the flap boundary layer as this flow is transferred through the cove area, consequently inducing flap flow separation. Overall, the findings provide valuable insights into propeller-wing-flap interactions, which had not been visualized before in this detail, yet emphasizing the need for further research to confirm and expand on these results.