On the Effect of Tip Flow on the Noise of a Ducted Rotor

This study focuses on the aeroacoustic aspects of ducted rotors that could possibly be used in future electrically driven helicopter tail rotor systems. It provides a comprehensive understanding of the tip flow evolution, and of the interaction with the stator stage. High-fidelity compressible numerical simulations are performed and compared with experimental results. A periodic variation is seen in the aerodynamic performance of the rotor blades, which is associated to a potential-interaction phenomenon. Additionally, the convection of the tip vortices and further impingement in the stator vanes generate torque fluctuations on these elements. Dilatation fields and Prms contours confirm a noise source generated by the tip-vortex–stator interaction. Finally, excellent far-field noise comparisons between the numerical and experimental results are obtained for both tonal and broadband noise.