Experimental Investigation of The Aeroacoustic Interaction Effects of Installed Pusher Propellers

This paper presents the results of the Clean Sky ERaCLE project regarding the experimental investigation of a pusher propeller configuration installed on a wing. Experiments were conducted in the acoustically treated open section Pininfarina Wind Tunnel in Italy. Aerodynamic and aeroacoustic tests were carried out on a wide range of airframe configurations, changing the relative distance between the propeller axes, the distance with respect to the wing and the relative phasing. The influence of the incidence angle was also investigated. Different noise emissions from the installed inboard and outboard propellers were reported. The thrust influence on the installed inboard propeller was also studied, varying the blade pitch angle. The polar directivity is reported for emission angles from 40° to 140°. The directivity pattern is mainly influenced by the scattering from the wing, with the propeller contribution limited around the disc area and downstream. Furthermore, a beamforming source localization technique is applied to identify the dominant sound sources, found to be located at the propeller tips, in the areas where they interact with the wing.