Numerical Study on the Aerodynamic Performance and Noise of Composite Bionic Airfoils

Bionic airfoils are an effective method to improve aerodynamic performance and reduce the noise of wind turbine blades. To explore the impact of the lower surface of bird wing airfoils on the aerodynamic performance and noise of blades, this study combines the upper surface of the NACA0018 airfoil with the lower surfaces of the teal, long-eared owl, and sparrowhawk (CBA-T, CBA-O, CBA-S) to create three new composite bionic airfoils (CBAs). The aerodynamic performance of these airfoils is evaluated, and the CBA-O airfoil is identified as having the best aerodynamic characteristics. A comparison of the noise and vortex structures of the CBA-O, owl wing airfoil, and NACA0018 is conducted, and the mechanisms behind the CBA-O airfoil performance improvement and noise reduction are explored. The results indicate that the CBAs enhance the aerodynamic performance of the airfoils. Before stall, the aerodynamic performance of the CBA-O improves the lift-to-drag ratio by 12.7% and 119.7% compared to the owl and NACA0018 airfoils, with its average SPL significantly lower than that of the NACA0018. The CBA-O has smaller vortex sizes at the trailing-edge, and the wake vortex develops more stably, effectively reducing both surface radiation noise and wake noise.