Validation of dynamic response of a 2-MW hybrid-spar floating wind turbine during typhoon using full-scale field data

Accurate estimation of the dynamic behavior of Floating Offshore Wind Turbines (FOWTs) under typhoon environment is essential to design and install FOWTs in a prone area of typhoons such as around Japan. Up to now, extensive efforts for development of design tools for FOWTs have been made, and nowadays several design tools are available. Needless to say, it is of utmost importance that the engineering design tools have been verified and validated for the real physical phenomena before being applied to real designs/projects with confidence. Much efforts have thus been made as code-to-code comparisons and by validations using model test data. Validations of the design tools using full-scale field data for FOWTs have also been made, but available open literatures are quite limited, particularly for design-driving extreme cases. In this paper, we describe the analysis of the dynamic response of a 2-MW spar-type FOWT at the time of typhoon attack in the actual sea area. The central atmospheric pressure of the typhoon at the closest time was 965 hPa, the maximum instantaneous wind speed at the hub height was 52.2 m/s, and the maximum significant wave height was 6.9 m. The dynamic responses under the typhoon environment are numerically simulated by using the time-series records of the wind speed, the wind direction, the wave height, the wave direction, the current speed, and the current direction which were acquired during the typhoon passing through close to the FOWT. Then the simulated motion responses are compared with the measured motion responses for the same durations. By the comparisons, the numerical simulation tool which was used for the design of the FOWT has been partially validated. It has also been confirmed that the spatial coherence of the wind speed has a significant effect for the platform motions, particularly for yaw motion.