AN EXPERIMENTAL INVESTIGATION OF TURBULENT BOUNDARY- LAYER INTERACTION WITH DIFFERENT SERRATED TRAILING-EDGE CONFIGURATIONS

The paper presents an experimental investigation of a turbulent boundary-layer interaction over a single large triangular serration at the Trailing-Edge (TE) of an airfoil on the flow-induced noise. Experiments were conducted at low-to-moderate Reynolds number given by 1.8 105 < Rec < 5.7 105, where c is the chord of airfoil. Six different TE serration geometries were studied: Three serrations with a single large triangular geometry at the TE, two serrations with varying orientation relative to the airfoil, and a straight-edged reference plate (in which the TE triangular serration is not considered). The airfoils with different TE configurations were placed in an anechoic wind tunnel in amean flow field with free-stream velocities of 25, 30 and 35 ms1. The radiated acoustic pressure field was recorded using a spiral microphone array located in the far-field. It was found that a significant noise reduction up to 6 dB was obtained when the included angle of the triangular serration was lessthan 45,which was in agreement with Howe’s theory. The Conventional Beamforming (CB) source maps confirmed that the noise reduction was obtained by varying the included angle of the triangular serrations. It was observed that the maximum noise attenuation occurred at frequencies above 5 kHz, where the TE noise dominates over the Leading-Edge (LE) noise. For frequencies below 5 kHz, the LE noise sources dominate over the TE noise