Aerodynamic and Aeroacoustical Characteristics of Low Reynolds Number Two-Dimensional Airfoil Flows

Abstract

Presented in this paper are measured data of aerodynamics of a NACA 0012 airfoil and resulting far-field sound at a Reynolds number of 2×105 to 5×105 and angle of attack of lifting case around maximum lifting to deep stall case Overall level of the generated sound gradually grows with increase of the angle of attack until maximum lift angle, and suddenly increases when the airfoil is stalled. Then, the overall level of the sound decreases when the angle of attack is further increased. In the maximum lifting condition, the measured surface pressure showed short bubble formed on suction surface of the airfoil and most contributions to the far-field sound come from a Strouhal number range of 1 to 20. In the light stall condition, long bubble is formed on suction surface, and the measured sound spectra monotonously decay. In the deep stall condition, the long bubble is disappeared and aerodynamic sound decreases in the frequency range between low frequency and middle frequency except for a weak peak at a Strouhal number of near the 0.6.