Comparison of Second-Order Loads on a Semisubmersible Floating Wind Turbine

Jason Jonkman, Sébastien Gueydon, Tiago Duarte

Research output: Contribution to conferencePaperpeer-review

44 Scopus Citations


As offshore wind projects move to deeper waters, floating platforms become the most feasible solution for supporting the turbines. The oil and gas industry has gained experience with floating platforms that can be applied to offshore wind projects. This paper focuses on the analysis of second-order wave loading on semisubmersible platforms. Semisubmersibles, which are being chosen for different floating offshore wind concepts, are particularly prone to slow-drift motions. The slack catenary moorings usually result in large natural periods for surge and sway motions (more than 100 s), which are in the range of the second-order difference-frequency excitation force. Modeling these complex structures requires coupled design codes. Codes have been developed that include turbine aerodynamics, hydrodynamic forces on the platform, restoring forces from the mooring lines, flexibility of the turbine, and the influence of the turbine control system. In this paper two different codes are employed: FAST, which was developed by the National Renewable Energy Laboratory, and aNySIM, which was developed by the Maritime Research Institute Netherlands. The hydrodynamic loads are based on potential-flow theory, up to the second order. Hydrodynamic coefficients for wave excitation, radiation, and hydrostatic forces are obtained with two different panel codes, WAMIT (developed by the Massachusetts Institute of Technology) and DIFFRAC (developed by MARIN). The semisubmersible platform, developed for the International Energy Agency Wind Task 30 Offshore Code Comparison Collaboration Continuation project is used as a reference platform. Irregular waves are used to compare the behavior of this platform under slow-drift excitation loads. The results from this paper highlight the effects of these loads on semisubmersible-type platforms, which represent a promising solution for the commercial development of the offshore deepwater wind resource.

Original languageAmerican English
Number of pages12
StatePublished - 2014
EventASME 2014 33rd International Conference on Ocean, Offshore and Arctic Engineering, OMAE 2014 - San Francisco, United States
Duration: 8 Jun 201413 Jun 2014


ConferenceASME 2014 33rd International Conference on Ocean, Offshore and Arctic Engineering, OMAE 2014
Country/TerritoryUnited States
CitySan Francisco

Bibliographical note

See NREL/CP-5000-61162 for preprint

NREL Publication Number

  • NREL/CP-5000-63497


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