Wind turbine blade vibration at standstill conditions - the effect of imposing time lag onto aerodynamic response

摘要

Aeroelastic codes used for full-turbine computations assume quasi-steady aerodynamics at standstill when the blades are in deep stall. Under these conditions these codes often show negatively damped edgewise blade vibrations. On the other hand, it is unlikely that the real-life aerodynamic response in deep stall is quasi-steady. This work focuses on analyzing how the aerodynamic damping is influenced by temporal lag in aerodynamic response. Therefore, it investigates whether it is inaccurate to model turbines at standstill with present aerodynamic codes. This is achieved by introducing different amounts of temporal lag onto aerodynamic response of an elastically-mounted-airfoil model. Both the time-domain and frequency-domain analyses show that aerodynamic damping is significantly increased even when relatively low amount of lag is introduced in the model. This indicates that the aeroelastic codes may overpredict edgewise vibrations in deep stall.