Experimental Characterisation of Cylinder-Induced Turbulence Ingestion in Propellers Operating in Edgewise Flight

The present paper investigates the aerodynamic and aeroacoustic characteristics of a propeller-wake interaction configuration comprising an upstream cylinder and a propeller in edgewise flight conditions. Through the use of experimental techniques within an anechoic wind tunnel, both the azimuthal and polar far-field noise characteristics were collected and analysed for a propeller in laminar and wake ingesting flight conditions. At lower inflow velocities, the aerodynamic forces were not observed to change significantly in the cylinder ingestion case. A more noticeable impact on the aerodynamic performance was noted as the inflow velocity increased. Far-field noise results indicate fundamental differences in the sound pressure level spectra whilst a cylinder wake is ingested by the propeller. A complex form of Haystacking appears in the blade passing frequency and its higher harmonics, showing evidence of both red- and blueshifting behaviour. Notable overall sound pressure level changes are also observed along with changes to the blade passing frequency directivity.