Investigation of Counter Rotating Open Rotor Orthogonal Blade/Vortex Interaction Noise

This paper investigates the influence of vortex models on the noise radiated by the orthogonal interaction of a rotating blade with a prescribed vortex. The blade motion, the vortex maximum velocity and core radius are set to produce an interaction representative of the ones occurring on a counter-rotating open-rotor at takeoff condition where interaction noise is prominent. Different compressible vortex models are considered. Links are made between radiated noise and the vortex velocity profiles. It is shown that velocity decay in the free-vortex region has a strong impact on the noise radiated at low frequencies while the inner structure of the vortex influences the acoustic spectra content at high frequencies.