Aeroacoustic and aerodynamic measurements at the rotor plane in the interaction of a small rotor with wings.

Abstract

Current research on tiltrotor noise predominantly concentrates on configurations with high disk loading and Reynolds numbers, leaving smaller aircraft setups underexplored. This study investigates aeroacoustic and aerodynamic trends resulting from rotor-wing interaction at low disk loading (<100 N/m2) and Reynolds number (Re < 100 000). The experimental setup comprises an anechoic chamber housing a two-blade rotor, flat and National Advisory Committee for Aeronautics 0012 airfoil wings, an ATI mini 40 load cell for aerodynamic data acquisition, and microphones positioned at the rotor height and installed on a rotation stage for acoustic data capture and directivity check. Investigated factors encompass rotor height, rotation direction, revolutions per minute (RPM), and wing curvature. Contrary to expectation, wing curvature does not visibly impact rotor performance. However, the deflected rotor wake in rotor-wing interaction markedly amplifies low-frequency broadband noise and the overall sound pressure level for the tested scenarios. The presence and strength of the deflected rotor wake tend to obscure the primary tonal noise and mitigate the effect of rotor RPM at smaller rotor spacings. This study provides valuable insights into mitigating noise resulting from rotor wake impingement on the wing in smaller aircraft configurations, contributing to the ongoing evolution of urban air mobility design considerations.