Experimental Aeroacoustic Characterization of a Supercritical Wing-Tip Model

An experimental aeroacoustic study of a blunt-tipped wing was performed in a Kevlar-walled test section to investigate the noise generation mechanisms at the wing tip. The model was a supercritical airfoil with a 0.305 m chord and an aspect ratio of 1.8, tested at the tunnel speed of U=50 m/s. The wing tip was found to generate a system of three vortices that form along the airfoil tip, as measured with stereo-Particle Image Velocimetry in the cross-stream planes. Surface pressure measurements showed pressure fluctuations originating from three different sources, which were identified to be associated with leading edge noise, and the unsteady velocity from the primary and secondary tip vortices. The dominant frequencies of the pressure fluctuations for each of these sources were documented over a range of angles of attack. The source maps of the far-field noise indicated the noise originating from the leading edge and the trailing edge area to behave consistently with the surface pressure fluctuations at their respective sources, suggesting their causal relationship. Finally, a comparison of the integrated spectra for different noise sources showed that the leading edge noise dominates the wing tip noise at the high-frequency range, whereas the primary and the secondary vortices generate noise at a lower frequency range. The integrated spectra showed that the contribution of the sound radiating from the wing tip to the total noise increased at higher angles of attack.