Experimental characterization and analytical modelling of rotor tonal noise

International audienceIn this study, the tonal noise due to the interaction ofa simplified rotor and a circular tower is characterized experimentally in a controlled environment. The test bench isinstalled in the anechoic chamber of ENSTA Paris, and is composed of a rotor made of three NACA 0012 untwisted blades set into motion by a motor. The radiated noise is measured by three microphones and 32 pressure taps are mounted on the tower wall to measure the pressure variation during the blade passage. The effect of the blade-tower distance is clearly captured in the wall and acoustic pressure measurements, blade-tower interaction noise being significant when the distance is smaller than the towerradius. Based on the measured wall pressure distribution on the tower surface, the acoustic pressure is calculated using Curle’s analogy in the compact far-field approximation. The contribution of the blades in the noise generationis not considered. The measured and predicted spectra arein good agreement, although the magnitude of the Fourier series coefficients of harmonics 3 to 6 tends to be overpredicted