Numerical investigation on flow separation control of dynamic stall over an airfoil using a fluidic oscillator

During the operation of rotorcraft and wind turbines, dynamic stall can lead to severe aerodynamic issues, including drag surge, lift loss, and unsteady loading. To address these challenges, this study proposes a novel active flow control method that employs a fluidic oscillator (FO) installed at the leading edge of a periodically pitching airfoil to mitigate dynamic stall. Numerical simulations are conducted based on two-dimensional unsteady Reynolds-averaged Navier–Stokes equations coupled with the Reynolds stress turbulence model. First, the fundamental characteristics and oscillation mechanism of the jet produced by the FO are thoroughly analyzed. Subsequently, the flow behavior over the baseline airfoil (without FO) and the airfoil with an inactive FO is investigated. The dynamic stall control process induced by the oscillating jet is then examined in detail. For comparison, a case with direct jet excitation is also studied. The flow control mechanism is elucidated by systematically analyzing the formation and evolution of spanwise vortices generated through the interaction between the jet and crossflow—identified as the dominant factor in flow control. Additionally, the control authority of the FO is evaluated. It is found that the FO effectively mitigates dynamic stall. Compared to the baseline case, FO implementation enhances the suction peak on the upper surface, reduces the aerodynamic hysteresis loop within a pitch cycle, and increases the average lift coefficient by approximately 7.6%. In contrast, the direct jet shows limited impact on dynamic stall control.