Influence of the rotor blade pitch angle on the far-field noise emissions of a ducted tail rotor

The present study focuses on the aeroacoustic aspects of ducted rotors that could be possibly used in future helicopter electrically driven tail rotor systems. Directivity measurements of the far-field acoustic pressure in the anechoic wind tunnel at Université de Sherbrooke have been performed varying the pitch angle of the rotor blades while maintaining the same rotational speed. The far-field noise shows a dominant tonal contribution over the whole audible frequency range. A level increase is seen when using the Pk109 configurations as well as the appearance of sub-harmonic humps. Also a broadening of the wake produced by the system is seen from the directivity plots. Preliminary results for the experimental campaign are achieved while the numerical simulations are achieved for one pitch angle and currently running for the other.