Numerical study on vortex-induced vibration of wind turbine airfoil at high angle of attack via free vibration simulation

Abstract

Dynamic response of an elastically mounted wind turbine airfoil at 90° angle of attack is investigated with free vibration simulation. The airfoil motion and unsteady aerodynamic force due to vortex shedding couple with each other, possibly resulting in vortex-induced vibration. This situation may be encountered during wind turbine parking or idling operations, which potentially leads to structure damage. Considering the frequency lock-in phenomenon of the vortex-induced vibration, the shedding frequency will synchronize with the structure natural frequency that could cause limit cycle oscillations. The frequency lock-in range of the elastically mounted airfoil is first determined by employing the free vibration simulation. The amplitude and stability of the limit cycle oscillation predicted based on the aerodynamic damping solved by the prescribed vibration simulation are in good agreement with the free vibration simulation. The transient process of the vortex-induced vibration is illustrated for different incoming velocities, airfoil mass, and initial positions. The aerodynamic damping is proven an efficient way to understand and predict the complex aeroelastic behavior during vortex-induced vibration.