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Experimental Assessment of Aerodynamic Noise on an Airfoil Surface

This paper describes the aerodynamic noise measurement method on an airfoil surface in laboratory conditions with non-standard equipment. The experiment and the measurements were performed in closed subsonic wind tunnel at the Aerodynamic Laboratory of Faculty of Transport and Traffic Sciences, University of Zagreb. To complete the measurement set, a charge amplifier and 3D printed airfoil model with six simple piezoelectric sensors were designed. The sensors were used for the airfoil surface noise assessment at different angles of attack and air stream velocities in the tunnel. After relayed through 6-way selector switch, the signal from each sensor under various conditions was suitably conditioned by the charge amplifier and recorded on PC for post-process data analysis. The paper gives the results of FFT analysis and offers discussion about observed correlations between absolute value of angle of attack and low frequency noise levels and spectra, especially prominent while gradually approaching critical angle of attack, the point where stalling of the airfoil occurs.

aerodynamic noise, acoustics, piezoelectric transducers, sensors, condition amplifiers, airfoil NACA 2421, experimental measurements, FFT analysis

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