Regular and Nonlinear Dynamics of Horizontal Axis Wind Turbine Blades Subjected to Fluctuating Wind Loads

This research investigates the nonlinear behavior and diagnosis of the nonlinear behavior of the horizontal axis wind turbine blades under fluctuating wind loads. Geometric nonlinearity of a blade and the nonlinear rotation of the blade subjected to the combined excitations of aerodynamic forces, elastic forces, and inertia forces including Coriolis forces are considered in the investigation. Various types of responses of the blades are found, including periodic, nonperiodic, quasiperiodic and chaotic vibrations, corresponding to the fluctuating wind loads. The influences of different external excitations due to the wind loads on the nonlinear responses of the blade are examined. The nonlinear responses of the blade are quantitatively characterized with the newly developed Periodicity-Ratio (P-R) method and the results are compared with that of Lyapunov Exponent method. The present approach shows efficiency and accuracy in comparing with the other approaches of nonlinear vibration characterizations.