Experimental and Computational Investigations of Propeller Wing Interactions for Varying Propeller Tilt Angles

A joint experimental-computational research campaign is underway to develop physical understanding and a validation-quality database for a model-scale tractor propeller-wing system. Separate load measurements on the wing and propeller accompany wing surface pressure distributions and flow field measurements via stereoscopic particle image velocimetry (SPIV) at discrete wing spanwise locations for a range of static propeller tilt angles. The physical wind tunnel test is modeled using a high-fidelity computational approach (Helios). Computational simulations aid in assessing the influence of the wind tunnel facility effects and test support structure wake interference, as well as in reducing uncertainties in the physical experiments for use in computational validation. The behavior of the induced thrust and lift at a zero-degree wing angle of attack in the axial flow regime (cruise configuration) is correlated with flow field measurements, showing distinct differences between upwash and downwash fields produced by the propeller. Recirculation regions near the wing upper surface are identified for high propeller tilt angles as the propeller wake interacts with the wing boundary layer. Increased propeller tilt angles result in a decreased wing lift and increased propeller thrust in forward flight, resembling a rotor in ground effect. Results indicate ways to improve computational modeling and refine the physical wind tunnel testing. These will be applied to refine the database to further elucidate physical understanding of the propeller-wing interactional aerodynamics.