Experimental on self-noise control of airfoil with ridge-like structure

This paper presents an experiment investigation of acoustic properties for NACA0012 airfoil at different freestream velocities with 0°and 10°angle of attack（AOA）. The acoustic wind tunnel test results show that at the freestream velocities of 30-60 m/s and AOA= 0°，the dominant noise is broadband noise，but at AOA=10°，the dominant noise is switched into tonal noise，and the tonal frequency is close to the Arbey acoustic feedback model. In order to eliminate the tonal noise of airfoil，a flow control method using a ridge-like structure to break the acoustic feedback loop is proposed，and the influence of the position and arrangement of the structure on the noise reduction performance is discussed. The results show that the closer the structure is to the leading edge of the airfoil，the more obvious the noise reduction effect is. With the increase of speed，the ridge-like structure in the back position no longer has a noise reduction effect in turn. In addition，the generation of tonal noise seems to be only related to the flow state of the pressure surface. When the flow state of the pressure surface is broken by the ridge-like structure，an effective feedback loop cannot be formed. Finally，based on the Arbey acoustic feedback theory，the differences in noise reduction performance of ridge-like structures are explored. It was found that when the ridge-like structure is located before the maximum speed point of the blade pressure surface，it can effectively intervene in the flow field to suppress the generation of monophonic noise. © 2024 Editorial Board of Jilin University. All rights reserved.