Comparison of various integrated coupled analysis methods for the semi-submersible floating wind turbine
Since wind turbine manufacturers generally only provide structural loads of wind turbines but do not disclose the superstructure parameters of wind turbines,carrying out the fully coupled analysis of floating wind turbines is quite difficult in the floating platform design of offshore wind turbines.From the viewpoint of wind turbine load components,fully-coupled,limited-coupled,quasi-coupled,and semi-coupled models are developed in this study.With"CNOOC Guanlan"as an example,a comparison study is conducted to reveal the differences of these models in calculating motions and mooring tensions of the floating wind turbine under extreme sea conditions.The results show that the maximum relative error between the results of fully-coupled model and those from the limited-coupled model which neglects the mass properties of wind turbines exceeds 70％.Thus,the limited-coupled model is not applicable for engineering applications.The maximum relative error of responses between the quasi-coupled model and the fully-coupled model is about 6％,while that between the semi-coupled model and the fully-coupled model is less than 2％.In other words,both the quasi-coupled model and the semi-coupled model meet engineering requirements.The quasi-coupled model,requiring only basic structural parameters of wind turbines and tower base loads of fixed wind turbines,is appropriate for conceptualization and preliminary design stages.The semi-coupled model can be employed during detailed design phases in collaboration with wind turbine manufacturers.Moreover,compared with the fully coupled model,the quasi-coupled model significantly improves computational efficiency by nearly three times,enabling rapid iterative optimization of floating platforms.This methodology has been implemented in the"CNOOC Guanlan"project and can be extended to the design of other semi-submersible floating wind turbines.
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