Coupled Blade-Hub Dynamics in Large Horizontal-Axis Wind Turbines

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The goal of this project is to deepen our understanding of the dynamics of horizontal-axis wind-turbine blades, and the loads that they impart to the gearbox and bearings, ultimately to provide guidelines for wind-turbine designers to develop turbines with significantly higher reliability. A wind-blade dynamic model involves effects of rotation, cyclic excitations due to gravity and steady wind shear (producing both parametric and direct excitation), aeroelasticity, and arbitrary wind-gust excitations. This work is focused on the resonances and instabilities associated with nearly identical wind blades coupled through the hub. Such symmetric arrangements are prone to vibration localization, which increases the vibration of a single blade. This project addresses these dynamics with fundamental modeling of the blades and hub, reduced-order modeling and perturbation analysis which yields the role of parameters and mechanisms underlying critical behaviors, high fidelity simulation studies that include the imparted loads on gears and bearings, and correlation of simulated events with field observations as available from the National Renewable Energy Laboratory and Sandia. This study will provide insight to the unknown dynamic loadings that can contribute to premature wind-turbine failures. The work thus enables a more reliable and cost-effective wind-energy fleet, which in turn promotes diversification of the renewable energy supply and the reduction of greenhouse gases. Understanding of resonances, localization, and instability of coupled blades with direct and parametric cyclic and aeroelastic excitation, and the effects on dynamic loading of the gearbox, will provide improved design guidelines for wind-turbine engineers, and will also advance the field of dynamics. Results will be disseminated through journal publications, conference presentations, and wind energy meetings and workshops. A doctoral student and an undergraduate will be prepared for the wind energy workforce. The PI will conduct outreach through existing university programs for high-school students and gifted middle school students.