One damping estimation approach of the parked offshore wind turbine supported by wide-shallow bucket foundation

The damping characteristic has an important influence on reliably predicting the dynamic response and fatigue life of the support structure of an offshore wind turbine (OWT). Generally, the damping sources of an OWT in parked conditions always include hydrodynamic damping, structural damping, and soil damping, ignoring aerodynamic damping. However, the difficulties in identifying the total damping of the OWT have created uncertainty and variation in the value of damping recommended in the design. In this research, an estimation approach for total damping was proposed for an OWT supported by a wide-shallow bucket foundation (WSBF), which is considered a novel bucket foundation, and its damping characteristics are still unclear. The hydrodynamic damping calculated based on Morison's equation of 0.0128% for the OWT supported by WSBF is smaller than the value of the monopile foundation. The soil damping is approximately 0.120%, obtained using the proposed theoretical method. Finally, the computational damping of the OWT in parked conditions was verified by the measured total damping of two parked OWTs at two different offshore wind farms (OWFs) of China. The results show that the damping obtained by these two methods was in good agreement with the average deviation of 11.20%.