Physics of the Interactional Proprotor-Wing Aerodynamics During the Tiltrotor Conversion Maneuver

This paper presents findings from a joint computational-experimental venture that seeks to advance the physical understanding and validation-quality database for a model-scale generic tractor proprotor–wing system during the tiltrotor conversion maneuver. This study evaluates the interactions in a quasi-static manner for various proprotor tilt angles (θ) across the tiltrotor conversion maneuver. Independent experimental measurements of the wing and proprotor loads accompany synchronous wing surface pressure measurements along with stereoscopic particle image velocimetry flow field measurements at discrete spanwise locations. High-fidelity computational fluid dynamics simulations leverage the multi-disciplinary rotorcraft simulation tool CREATE™-AV Helios to assess the interactional aerodynamics of the proprotor–wing configuration across the tiltrotor conversion maneuver. Computational simulations use a newly implemented Helios module to trim to the experimental proprotor thrust. Validation of the computational model, along with a mesh refinement study, is shown via comparison of the integrated proprotor and wing loads as well as wing surface pressure distributions. The validated computational model is used to examine the proprotor-to-wing aerodynamic interactions further. For low proprotor tilt angles (0° ≤ θ ≤ 30°), interactions between the wing boundary layer and proprotor wake results in the breakdown of the wake along the wing chord. For moderate proprotor tilt angles (45° ≤ θ ≤ 60°), the interactions are dominated by the proprotor tip vortices curling around the wing leading edge. Approaching edgewise flight (75° ≤ θ ≤ 90°), the predominant proprotor–wing interactions stem from standing vortices on the wing upper surface, producing strong low-frequency responses on the wing. Overall, this work introduces new insights into the complex proprotor–wing aerodynamic interactions across the tiltrotor conversion.