Bidirectional Vibration and Fatigue Mitigation of a Barge-Type Floating Offshore Wind Turbine Using an Omnidirectional Tuned Mass Damper

This paper investigates the mitigation of bidirectional vibrations and induced short-term fatigue in a 5 MW barge-type floating offshore wind turbine (FOWT) subjected to stochastic misaligned wind and wave loadings. To address this challenge, a passive omnidirectional tuned mass damper (OTMD) integrated within the barge floater is proposed as a vibration suppression strategy. First, a comprehensive dynamic analysis was conducted under realistic environmental conditions using the coupled aero-hydro-servo-elastic simulation tool OpenFAST to identify the critical vibration modes of the FOWT. Next, various TMD calibration techniques were reviewed to determine the most suitable tuning approach to be used for the mitigation of bidirectional dynamic responses. The performance of the calibrated OTMD was evaluated under both operational and parked conditions. Mitigation performance under operational condition was assessed in terms of vibration reduction, short-term fatigue and peak nacelle acceleration under long-crested (unidirectional) and short-crested (multidirectional) wave excitations. Additionally, the TMD effectiveness during extreme parked scenarios triggered by gust-induced fault followed by emergency shutdown was evaluated, focusing on vibration and peak response attenuation. The observed mitigation performance was found to be strongly influenced by aerodynamic damping, as reflected in the OTMD motion within the barge floater. Overall, the results demonstrate the viability of using a passive omnidirectional TMD to reduce bidirectional dynamic responses in floating wind turbines.