Experimental investigation of unmanned air vehicle rotor aeroacoustics using benchmark geometries

A series of benchmark and off-the-shelf unmanned air vehicle rotors with diameters around 12 inches was tested in the newly-built anechoic chamber at the Łukasiewicz Research Network - Institute of Aviation, as well as in an open field. The aerodynamic performance of the rotors was assessed using thrust and torque meters embedded in a custom testing rig, and their acoustic characteristics, including directivity, were determined using a column of free-field microphones. The characteristics of the anechoic chamber, including the spatial distribution of background noise and the anechoic condition, were evaluated in detail, and the comparison with open-field measurements enabled confirmation of its suitability for testing of low Reynolds number rotors. The measurements of rotor performance were compared with published results, and the agreement between the data sets validated the methodologies employed in this study. Furthermore, a new benchmark is defined based on an 8-inch commercial rotor, for which broadband noise is more significant than for larger diameters. A full set of aeroacoustic characteristics is presented, broadening the range of available benchmark cases.