Experimental Analysis of Rotor Blade Noise in Edgewise Turbulence

This paper presents an experimental investigation into the effects of turbulence ingestion on aerodynamic noise characteristics rotor blades in edgewise flight. A small-scaled, two-bladed was used study. The test utilised two turbulence-generating grids, to generate inflows with different characteristics, and compare them baseline configuration laminar inflow. experiments were set at forwarding flight configuration, freestream inflow velocity ranging from 10 m/s 22 m/s. Simultaneous measurements far-field acoustic pressure load conducted, along a separate flow measurement using particle image velocimetry. spectra demonstrated larger contribution tonal radiation blade passing frequency, broadband mid-frequency domain, due ingestion. However, responses high-frequency domain comparable between tested cases, similar humps featuring spectra. directivity patterns overall sound level showed that lowest near plane rotation, highest downstream. Turbulence could also be seen elevated levels throughout observation positions for grid particularly advance ratios.