Study on Frequency Lock-in Phenomenon and Aeroelastic Stability of the Airfoil at High Angle of Attack

The frequency lock-in during vortex-induced vibration of airfoil at high angle of attack brings potential safety risks to flight safety. In this paper, the unsteady Reynolds-averaged Navier–Stokes equations are used to simulate the prescribed pitching vibration of an airfoil at mean attack angle of 40◦, and investigate the frequency lock-in phenomenon during airfoil vibration. Based on the results of unsteady numerical simulation, the aero-elastic stability of the airfoil is evaluated by the average aerodynamic cycle work. The results show that the frequency lock-in region of pitching vibration isV shaped, in which the side with smaller vibration frequency has higher aerodynamic work, indicating risk of the vortex-induced vibration phenomenon. The increase of vibration amplitude delays the shedding of the trailing edge vortex during pitching, which reduces the aerodynamic work near the trailing edge of the upper surface and promotes the vibration to be stable. Phase space reconstruction and recurrence plots can capture the state difference of nonlinear dynamic system between frequency lock-in and unlock-in. © 2023 Science Press. All rights reserved.