Computational Study of the Aeroacoustics of a Circulation Control Airfoil

Circulation control is a promising method to augment the lift of airfoils and hydrofoils and enhance vehicle maneuverability. However, its acoustic effect is a significant concern and not well understood. In this study large-eddy simulations of a circulation control airfoil in a low-Mach-number flow are performed at a chord Reynolds number of 650,000 and three jet momentum coefficients. The acoustic radiation is calculated by solving the Lighthill equation using a boundary element method. The predicted sound pressure spectra show good agreement with the experimental measurements of Reger et al. (J. Sound Vib. Vol. 388, 2017). The Coanda jet is shown to suppress the low-frequency airfoil vortex-shedding noise, but at the same time causes a significant increase in broadband noise in the mid-to-high frequency range. The amount of increase grows with the jet momentum coefficient. High-frequency tonal noise is generated as a result of strong vortex shedding from the slot lip, and its magnitude and frequency also increase with increasing jet momentum coefficient.