Localization of airfoil self-noise sources by a virtual phased microphone array technique

Phased microphone array technique has received much attention for the localization of sound sources in various acoustic experiments. In this paper, this technique is adopted to locate airfoil self-noise sources at low Mach number and moderate Reynolds number flows based on a high order Computational Aeroacoustics (CAA) data base. Both the near-field hydrodynamics and the far-field acoustics are computed simultaneously by a Direct Numerical Simulation (DNS) method. In particular, the time-resolved data on a virtual phased microphone array in the acoustic far field is sampled and analyzed using beamforming algorithms. The effect of the angle of attack on the acoustic source location and strength is evaluated by phased array calculations. The results show that for frequencies between 3000 and 4000Hz the dominant noise sources of airfoil self-noise is located at the airfoil trailing edge region which is independent of the angle of attack. While for relatively higher frequencies between 4000Hz and 6000Hz, the acoustic sources start to move downstream for zero angle of attack and move upstream for two and four degrees angle of attack. The strength of the acoustic sources also increases with the increasing of airfoil angle of attack.