Numerical Study of Airfoil Tonal Noise Reduction using Segmented Elastic Panel Configuration

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Abstract

In this paper, a novel passive method for airfoil tonal noise reduction is proposed using a configuration of two segmented elastic panels mounted on the airfoil. Numerical investigation using perturbation evolution method is carried out at a low Reynolds number based on airfoil chord of 5×10 and an angle of attack of 5. The passive method of employing a single panel has shown promising tonal noise reduction capabilities where the resonating panel located just ahead of the sharp growth of boundary layer instability within the airfoil separation bubble provided the strongest reduction of instabilities and noise reduction up to 3 dB has been achieved. The idea is extended in the present study by employing a two-panel configuration based on the localized flow characteristics over the airfoil surface. Five different panel configurations are designed and their effectiveness in terms of tonal noise reduction is evaluated and compared with baseline configuration. The azimuth and spectral analyses indicate the different extent of noise reduction for each configuration and even noise amplification in one of them. A significant noise reduction up to 8 dB is observed for the optimum configuration indicating the effectiveness of this novel method for devices operating at low Reynolds number.