Airfoil self noise reduction by application of different types of trailing edge serrations

The present paper will address the trailind edge noise reduction by the means of trailing serrations. An experimental study of the effect of adding three different geometries of trailing-edge serrations, to a two-dimensional NACA 0012 is presented. The wing model has 92 pressure tapings for aerodynamic analysis which was complemented with trailing edge boundary layer measurements using hot wire measurements. For aeroacoustic tests, an array with 106 microphones was employed to measure noise sources location, using a beamforming technique. The antenna is suitable for acoustic measurements up to 16 kHz. It was found that for realistic airfoil geometries overall self-noise reductions of 2-3dB are possible without adversely affecting aerodynamic performance. Nevertheless, the reduction in self-noise amplitude was found to be most significant at lower frequencies, and the effect became more pronounced with increasing wind velocity. It appears that applying serrations to the airfoil trailing edge is a valid means of reducing airfoil self-noise without compromising aerodynamic performance.