A parametric study of spar-type floating offshore wind turbines (FOWTs) by numerical and experimental investigations

The use of spar platforms as a substructure for floating offshore wind turbines (FOWTs) is a new concept that is developing quickly in the offshore wind industry owning to the excellent stability and adaptability to different water depths. However, the lack of studies about the dynamic response and design guidelines of spar-type FOWTs is a barrier to further development of the offshore wind industry. Therefore, the goal of this study is to carry out dynamic response analysis and to develop design guidelines for spar-type FOWTs. To achieve this goal, the dynamic responses of full-scale spar-type FOWT models with different values of three design variables (spar diameter, depth, and concrete ratio) were first numerically obtained in the time domain and experimentally validated by considering all environmental conditions such as wind, regular wave, and constant current loads, as well as the mooring line loads. Then, regression and perturbation analyses, which were also validated by the analysis of variance method, were performed to analyse the effects of the design variables and to propose design guidelines of spar-type FOWTs.