Noise Reduction Mechanisms due to Bio-Inspired Airfoil Designs

This paper presents numerical analysis of an airfoil geometry inspired by the down coat of the night owl. The objective is to understand the mechanisms of airfoil trailing edge noise reduction that has been observed with such designs in previous experiments. The bioinspired geometry consists of an array of “fences” that are applied near the trailing edge of the NACA-0012 baseline airfoil. Wall-resolved large eddy simulations are performed over the baseline and the bioinspired airfoil geometries and the aeroacoustic performance of the two geometries are contrasted. Both models are simulated at chord-based Reynolds number Rec = 5 × 105 , flow Mach number, M∞ = 0.2, and angle of attack, α = 0◦ . Farfield noise spectra comparisons between the baseline and the bioinspired airfoil near the airfoil trailing edge show reductions with the fences of up to 10 dB. The simulations reveal that the fences lift turbulence eddies away from the airfoil trailing (scattering) edge hence reducing scattering efficiency. These findings suggest that one of the mechanisms of noise reduction is the increased source-scattering edge separation distance