Aeroacoustic characteristics of distributed electric propulsion system in forward flight

This study presents a detailed experimental investigation of the aeroacoustic characteristics of distributed electric propulsion configurations in forward flight, with a focus on the effect of the blade tip separation distance between the propeller blades. Two identical 5-bladed propellers with a diameter of D = 9” and P/D = 1 were mounted on a NACA0018 wing, such that the wake from the propellers impinged directly on the wing. The effects of the blade tip separation distance were investigated while maintaining a constant rotational speed of 8000 rotations per minute. Measurements were acquired at fine increments of wind tunnel speeds ranging from 8 m/s to 16 m/s corresponding to various advance ratios. The spectra and directivity of the far-field noise were studied in detail for both broadband and tonal components.