Aeroacoustic source localization on open rotor aircraft model in wind tunnel tests

Phased Array aeroacoustic measurements are gaining an increasing interest in automotive and aeronautic design. This paper describes the beamforming approaches used for characterizing acoustic sources on an counter rotating open rotor (CROR) installed on a 1/7th scale model of an advanced regional air-craft design. The tests were conducted in a large Low Speed Wind Tunnel (WT) at The Pininfarina Aerodynamic and Aeroacoustic Research Center in Turin, Italy, within the framework of the FP7 EU Clean-Sky WENEMOR (Wind tunnel tests for the Evaluation of the installation effects of Noise EMissions of an Open Rotor advanced regional aircraft) project. Three planar microphone arrays were installed in Pininfarina WT: A wheel array (3m diameter) placed at the ceiling of the WT (Top), a half-wheel array positioned broadside and parallel to the axis of the open rotor (Lateral) and a spiral array (2.5m aperture) placed upstream the blade plane and at an angle of 10 degrees to the blade plane (Upstream). Measurements were performed for a variety of aircraft geometries (involving different fuselage and rotor configurations), angles of attack and wind speeds. Preliminary beamforming results obtained processing the Top and Lateral arrays are presented and discussed.