A numerical study on the delay of airfoil stall by traveling wave surface morphing*

Surface morphing is found to be an energy efficient active flow control technique. While these morphings are, typically, in the form of a simple vibration or a standing wave, a traveling wave morphing might to be more effective because traveling wave oscillations are thought to reattach the flow over aquatic swimmers and bluff bodies. Large eddy simulations (LES) of flow over a low Reynolds number (Re$=$50,000) airfoil at stall angle, which has a oscillatory suction side, are performed to investigate the effect of the morphing function, i.e., backward traveling waves, standing waves, and forward traveling waves, on reducing flow separation. In addition, the effects of frequency and amplitude of the wave are investigated. It has been observed that backward traveling waves can be more effective than other types of oscillations, including forward traveling waves and standing waves.