Passive flow control of a stalled airfoil using an oscillating micro-cylinder

Abstract

The effect of passive flow control using an oscillating micro-cylinder near the leading edge of a stalled airfoil (S809) at a Reynolds number of 1 × 106 is numerically investigated. A physical analysis of the flow fields is performed to illustrate the mechanisms of flow control for the improvement of airfoil aerodynamic performance. When the optimal parameters are selected, the research about the ability of suppressing the separation of the static micro-cylinder is studied at different angles of attack. The simulation results show that the static micro-cylinder can effectively suppress the flow separation and improve the aerodynamic performance of airfoil at angles of attack range from 10° to 24°. Then we replaced the static micro-cylinder with the oscillating one. The simulation results proved that when a static micro-cylinder cannot control the flow separation well, a better flow control effect can be achieved by the oscillating cylinder. Furthermore, the diameter of the oscillating micro-cylinder is smaller than the static one's when a same lift-to-drag ratio is achieved. Compared with the original S809 airfoil, the lift-to-drag ratio of the airfoil with an oscillating micro-cylinder can be increased by 88.21% at optimal oscillate method.