Passive structural control for wind turbine towers using a novel dual-track nonlinear energy sink

Abstract

With larger rotors and taller towers developed to capture more wind energy, the tower structures become slenderer and more sensitive to wind loads, resulting in vortex-induced vibration (VIV) in both downwind and crosswind directions. The vibration control is faced with the challenges of broadband and multi-directional dynamic responses. Thus, this paper proposed a new type of dual-track nonlinear energy sink (NES) aimed to achieve the multi-mode and multi-direction vibration control of wind turbine towers. The two-degree-freedom coupled governing equations of the wind turbine tower with the dual-track NES are established and solved numerically, with full considerations of aerodynamics and fluid–solid interactions. Then, an optimized design of the dual-track NES is performed theoretically. To evaluate the vibration mitigation performance of the dual-track NES, a series of wind tunnel tests are carried out and analyzed further, in terms of the acceleration time-history response, statistical characteristics, frequency and damping ratio. It is demonstrated that the proposed NES functioning as an energy-dissipating device is efficient and robust in mitigating the dynamic response of wind turbine towers, even enabled to address the vortex resonance. It is remarkable that the dual-track NES can synchronously realize the vibration control in multi-mode and multi-direction by increasing the damping ratio of primary structure.