Mode Localization In Linear And Periodically Time-Varying Mistuned Wind Rotor

Rotor blades are the most important and most expensive part of a wind turbine; their dynamic behavior is of great significance for maintenance planning and safe operation. In this study, the effect of mistuning on the vibration modes of rotor blades was investigated, with a focus on the mode localization of linear time-varying wind turbine rotors. And the significance of the work lies in finding that the mode localization may aggravate the blade damage and potentially reduced fatigue life of the blade. The rotating blades were approximated as cantilever Bernoulli-Euler beams, and the flapwise and edgewise modes of each blade were considered. The Lagrangian method was employed to derive the linear time-varying dynamic equations of the wind turbine rotor. A wind turbine rotor was mistuned because of slight fluctuations in the blade stiffness; subsequently, Floquet analysis was employed for modal decomposition of a mistuned wind turbine rotor, and the mechanism of mode localization was examined in depth. Numerical simulation results indicated that slight mistuning of a single blade is sufficient for triggering mode localization. The effects of the magnitude of the blade mistuning and rotor speed on the severity of mode localization were analyzed. Finally, different quantitative measures were considered for characterizing the degree of mode localization in mistuned wind turbine rotors.