Vibration reduction performance of a nonlinear energy sink installed in the platform of floating wind turbine

Abstract:

The trend towards larger offshore wind turbines has led to increasingly severe vibration issues for floating wind turbines operating in harsh sea conditions. The complex fluid-structure interaction and multi-mode vibration characteristics of such structures highlight the limitations of conventional passive vibration absorbers, which can only be tuned to a single frequency. To address this issue, this paper proposes the application of a nonlinear energy sink (NES) with broadband vibration reduction capability to the tension leg platform floating wind turbine (TLP-FWT), aiming to develop a novel vibration reduction strategy suitable for multi-mode responses. A dynamic model of the TLP-FWT-NES was first established based on D′Alembert′s principle, and its parameters were corrected using the Leven-Marquardt algorithm. Subsequently, the NES parameters were optimized through a combination of grid search and Bayesian optimization, and its performance was compared with that of a tuned mass damper (TMD). Finally, fully coupled numerical simulations under various sea states were carried out using the OpenFAST to comprehensively evaluate the vibration reduction performance of the NES. The results demonstrate that the NES exhibits greater robustness to stiffness variation than the TMD, through the mechanism of resonance capture cascade and targeted energy transfer, it can effectively suppress multiple vibration modes when high-order modes are selected as the optimization target. However, in single-mode control scenarios, the NES does not outperform the TMD, while under extreme sea states, both devices are capable of reducing structural vibration, with the TMD showing superior overall effectiveness. This study provides new insights into multi-mode vibration control of floating wind turbines and offers a useful reference for enhancing the operational safety and structural reliability of large-scale floating wind turbines under complex marine conditions.