Optimization of multiple rotational inertia double tuned mass damper for offshore wind turbines under earthquake, wind, and wave loads

This study introduces a framework for designing an optimal multiple rotational inertia double tuned mass damper (MRIDTMD) with multiple tuning frequencies to effectively mitigate vibrations in offshore wind turbines (OWTs) subjected to combined wind, wave, and seismic loads. The framework comprises a coupled numerical model of an OWT with an MRIDTMD, an intelligent optimization algorithm, and parallel computing technology. First, coupled governing equations of motion for an OWT with an MRIDTMD under seismic conditions are derived based on multibody dynamics and fully coupled analysis theories in FAST v8. Subsequently, an MRIDTMD submodule is developed and integrated into FAST v8 to establish a coupled analysis model for an OWT with MRIDTMDs using an updated simulation tool. Furthermore, an intelligent optimization algorithm and parallel computing technology are introduced to establish the framework, and the MRIDTMDs are optimized. Moreover, the efficiency of the optimized MRIDTMD is assessed based on observed reductions in the OWT responses under combined seismic cases. Subsequently, comparisons with an optimized multiple tuned mass damper (MTMD) and a parametric study are conducted. The effectiveness and robustness of the optimized MRIDTMD and the improved mitigation effects of the MRIDTMD compared with the MTMD owing to the additional inerter are proved.