Dual-Track Nonlinear Energy Sinks for Mitigating Bi-Directional Vibration of Wind Turbine Towers in Typhoons

Under typhoon attack, slender and lightly damped offshore wind turbine systems are prone to significantly exacerbated aeroelastic dynamic responses and increased structural instability risks, potentially leading to damage or collapse. To address the complex vibration challenges in multi-mode and multi-directional systems, this paper proposes a dual-track nonlinear energy sink (NES) and establishes a theoretical model for the wind turbine tower system coupled with the dual-track NES, incorporating blade rotation and vortex shedding effects. A comprehensive optimization of the dual-track NES is conducted to determine the optimal track profiles and damping ratios. An aeroelastically scaled model of the wind turbine tower system is designed and tested in typhoon fields simulated in wind tunnels. The effectiveness of the dual-track NES is evaluated under various conditions by analyzing acceleration time-history responses, displacement trajectories, frequency, and damping ratios. Experimental results demonstrate that the dual-track NES can effectively suppress the tower’s response in both alongwind and crosswind directions, with the displacement trajectory significantly narrowed, eigenvalues of displacement power spectral density reduced in orders, and damping ratio increased up to five times. Notably, under resonance conditions, the acceleration response is reduced by up to 97.1%, while in non-resonance conditions, the reduction can reach up to 79.4%. This innovative approach provides a promising solution for mitigating typhoon-induced multimodal resonances and avoiding dynamic instabilities in offshore wind turbine systems.