On the mechanism of acoustic resonances from a leading-edge slat

Implicit large-eddy simulations are performed to investigate the acoustic resonances from a leading-edge slat at two different Reynolds numbers. Three types of acoustic waves are identified in the vicinity of the slat, but only one is found to be amplified by fluid-acoustic feedback mechanism. With phase-averaged flow-fields, we clearly identify that the vortical structures in the slat cove are formed at the same frequencies of the observed acoustic tones. A fluid-acoustic feedback loop is confirmed between the formation of the discrete vortices and the radiation of low-frequency acoustic waves. A theoretical model is proposed and validated to predict the frequencies of low-frequency resonances at three angles of attack. High-frequency acoustic waves are also found to emanate from the slat-wake region and the suction side of the main wing. (C) 2021 Elsevier Masson SAS. All rights reserved.