On the airfoil self-noise reduction by trailing edge serrations of non-insertion type

Abstract

This paper represents the results of a preliminary study aimed at reducing the airfoil trailing edge self noise by employing non-insertion type trailing edge serrations. This configuration offers better structural strength and integrity, as well as more straightforward manufacturing process compared to the flat plate type serrations. We found that the noninsertion type serration can reduce the broadband self noise significantly. However, due to the presence of partial bluntness at the serration root, unwanted by-product such as the lowfrequency vortex shedding tonal noise can also be produced. This extraneous noise is found to be less significant if a larger serration angle is employed when the airfoil is set at an angle of attack. We further tested a hybrid configuration composing a non-insertion serration and a woven-wire mesh screen from which the low-frequency vortex shedding tonal noise can be further reduced alongside the broadband self noise reduction.