Effect of Wavy Leading Edges on Airfoil Trailing-Edge Bluntness Noise

Abstract

Among the several noise-generation mechanisms of airfoil self-noise, trailing-edge bluntness noise is an important noise source, which is caused by the vortex shedding at blunt trailing edges. A numerical study on airfoil trailing-edge bluntness noise control using the bio-inspired wavy leading edges is presented in this paper. The high-fidelity, improved, delayed, detached eddy simulation (IDDES) method was used to calculate the flow field, and the acoustic analogy method was used for noise prediction. For both the blunt-trailing-edge airfoils, a baseline airfoil with a straight leading edge and a bio-inspired airfoil with a wavy leading edge were used in this study. The chord-based Reynolds number was 400,000, and there was no angle of attack. The numerical results show that the trailing-edge bluntness noise of the baseline airfoil was significantly reduced by the wavy leading edges. The sound pressure level reduction was about 3.7 dB at the characteristic frequency, and the maximum sound pressure level reduction was as high as 35 dB. The trailing-edge bluntness noise was decreased at all directional angles. The maximum overall sound pressure level reduction was 6.3 dB at 0°. In addition, by analyzing the pressure fluctuations, wake characteristics, turbulent vortex structures and spanwise correlation and coherence of the flow field, the noise-reduction mechanisms of the bio-inspired airfoil are deeply revealed.