Numerical Investigation of Airfoil Self-noise Control by Trailing-edge Blowing

Large eddy simulation and Ffowcs Williams-Hawkings acoustic analogy are performed to study the effect of trailing-edge blowing on airfoil self-noise. The chord-based Reynolds number is 4 × 10 at a zero angle of attack for a NACA 0012 airfoil. Firstly, the aerodynamic and aeroacoustic characteristics of the baseline airfoil were thoroughly verified by comparison with previous numerical and experimental data. Secondly, the noise reduction effects of continuous and local blowing with different blowing momentum coefficients and blowing flow rate ratios were compared. Finally, a maximum noise reduction of 20 dB achieved via trailing-edge blowing is presented along with a discussion of the noise reduction mechanisms of the two blowing methods. The vortex shedding is suppressed by the blowing at the trailing edge, the shear layer at the trailing edge is stabilized, and instantaneous vorticity and root mean square velocity fluctuations are weakened. It is also found that there is a decrease in the spanwise coherence and an increase in the phase difference, which can account for noise reduction. The noise reduction mechanisms of blowing at the trailing edge can inspire further noise reduction by blowing.