Mechanism of the wavy leading edge on reducing the self-noise from a cambered airfoil at a moderate Reynolds number

The performance of the wavy leading edge (WLE) on the self-noise from a cambered NACA 65(12)-10 airfoil at a Reynolds number of 100 000 is investigated in this paper. The self-noise from the airfoils is measured in an anechoic wind tunnel while the flow details are obtained from both planar particle image velocimetry measurements and the wall-resolved large eddy simulations. It turns out that the WLE is effective in reducing both the tonal and the broadband separation noise in the mid-to-low-frequency range from the baseline airfoil. The underlying mechanisms of the noise reduction are also examined carefully from both the tonal and the broadband aspects. By introducing the WLE, the generated streamwise vortices can modify the boundary-layer development and reduce the spanwise coherence of the flow structures. As a consequence, the acoustic feedback loop responsible for the tonal noise from the baseline airfoil is disturbed. Additionally, the WLE decreases the convection velocity and generates less coherent wall pressure fluctuations in the low-to-mid-frequency range, leading to broadband separation noise reduction.