Airfoil self noise reduction by non-flat plate type trailing edge serrations

This paper represents the results of a preliminary study which aims to reduce the airfoil trailing edge self noise by employing non-flat plate type trailing edge serrations. This configuration offers better structural strength and integrity, as well as a more straightforward manufacturing process compared to the conventional flat plate type serrations. We found that the non-flat plate serration not only reduces the broadband self noise significantly, but also eliminates the high-frequency noise that was observed by others who used flat plate type serration. However, due to the presence of certain bluntness at the sawtooth root, vortex shedding noise in a narrow frequency bandwidth is also produced. This extraneous noise is found to be less significant if a wider-angle serration is used. To increase the effectiveness of the proposed serration geometry a hybrid configuration composed of a non-flat plate type trailing edge serration with woven-wire mesh screen is employed for the reduction of the narrowband vortex shedding noise.