Numerical study on aerodynamic performance and noise characteristic of several bionic airfoils

The bionic airfoils were restructured by extracting cross-section configurations of four species of bird wings at the 40% position along the spanwise direction respectively based on the airfoil theory. The flow fields and the corresponding sound fields over the designed bionic airfoils were simulated numerically by using large-eddy simulation coupled with the acoustic analogy of Ffowcs-Williams and Hawkings equation. The results on unsteady flow simulations indicated that the airflow separated at the leading edge of the suction side under the effect of adverse pressure. The vortex structure was formed at the downstream of the blade, and it broke down after it was separated from the tailing edge of the blade. The lift-to-drag ratio of seagull airfoil was the maximum and the lift-to-drag ratio of owl airfoil was the minimum, however, the later possessed excellent noise-reduction characteristic. The directional distribution of SPL revealed the dipole characteristics of the acoustic source of four bionic airfoils.