Experimental Study on Multiobjective Flow Control of Dynamic Stalls Using a Vortex Generator

The dynamic stall of the airfoil can adversely affect the performance of helicopter rotor blades, jet engine compressor blades, wind turbine blades, and so on. Therefore, the flow control on the dynamic stall is necessary. This paper conducted an experimental study on the multiobjective flow control effect of the dynamic stall on a NACA0012 airfoil using a passive vortex generator (VG). The control effect of the VG on the dynamic stall is discussed, and the control mechanism is explained. Within the scope of this paper, the VG could significantly increase the maximum normal force coefficient (Cn) by 0.223, reduce the peak negative moment coefficient (Cm) by 0.049, and delay the stall angle of attack of Cn and Cm by α=1.8° and 2.9°, respectively. These multiobjective control effects were attributed to the control of the complex vortices on the suction surface. The VG delays stall by suppressing the formation of the shear layer vortex, and enhances the aerodynamic performance during dynamic stall by energizing the dynamic stall vortex (DSV). The effects of the VG on the convection speed and strength of the DSV are additionally investigated from a space-time perspective. Within the reduced-frequency range studied in this paper, the DSV convection speed controlled by VG was smaller than that of the baseline airfoil, and the VG could significantly enhance the strength of the DSV.