Rod–Airfoil Interaction Noise at Different Rod Cross Sections and Airfoil Angles

Abstract

Vortex–body interaction noise from a rod–airfoil model has been investigated experimentally in an aeroacoustic wind tunnel. The model configuration varies by changing either the rod cross section (circular, square, rhombic, and elliptical) or the install angle of the airfoil at three directions (attack angle , sweep angle , and lean angle ) independently. This paper aims to assess the effects of these parameters on the characteristics of vortex–body interaction noise. A near-field microphone array was applied to locate the noise sources on the rod–airfoil model, and a far-field microphone array determined the noise level and radiation directivity. The results suggest that, in the test range, both the elliptical rod cross section and the change of the airfoil install angles can visibly reduce vortex–body interaction noise compared to the baseline rod–airfoil containing the circular rod and the airfoil at zero angles. The interaction noise level decreases with the increase of the eccentricity of the elliptical rod. Of the angles, the most effective way is the change of the sweep angle , which can achieve a noise reduction of 8 dB when reaches 20 deg, but the attack angle has more influence in reducing the vortex shedding frequency. In addition, the noise source distribution of different frequencies also changes with the variation of rod–airfoil configurations. Flow visualization using particle image velocimetry was conducted to analyze the noise change mechanism. The findings from this study are beneficial for engineers in designing low-noise components in several aeronautical and industrial applications.