Airfoil Trailing-Edge Blowing: Broadband Noise Prediction from Large-Eddy Simulation

Trailing-edge blowing has in recent studies found to be a potential technique for broadband noise reduction in turbomachinery applications with rotor-stator arrangement. The key-idea is to inject fluid into the wake of the rotor in such a manner that the wake will become momentumless and the turbulence structure will be modified by the enhanced mixing process. Ultimately, this wake manipulation should lead to a reduced aeroacoustic response of the downstream stator-vane with the modified turbulent wake of the rotor. The study presented within this paper investigates the trailing edge blowing mechanism by numerical means in a simplified configuration. A large-eddy simulation on a NACA 6512-63 airfoil without and with trailing-edge blowing is undertaken to investigate the effect of blowing on wall-pressure statistics of the blowing airfoil and also its wake turbulence structure and characteristics. The broadband self-noise of the airfoil is predicted by Amiet’s trailing edge noise theory. It appears that two competing mechanisms exist: a potentially increased airfoil self-noise due to the blowing jet interacting with the jet slot-lip and the trailing edge, and a reduction in interaction noise through manipulation of the wake turbulence and early wake-turbulence decay. Overall this study provides a first insight into some relevant parameters concerning the potential for broadband noise reduction through trailing-edge blowing.