Load sensitivity analysis for a floating wind turbine on a steel semi-submersible substructure

The site-specific load verification for floating offshore wind turbines requires the consideration of the complex interaction of the different system components and their environment. Sensitivity analyses help reducing the simulation amount for both fatigue and ultimate load analysis significantly by highlighting relevant load parameters and increase the understanding for the system behavior in its real environment. Aligned with work in the H2020 project LIFES50+, this study investigates different approaches for global sensitivity analysis using quasi-random sampling for the independent variables. Two different load case groups are analyzed: (1) fatigue loads during power production, (2) ultimate loads during power production and severe sea state. The considered system is the public DTU 10MW turbine’s rotor-nacelle assembly, installed on the public NAUTILUS-10 floating structure. Load simulations are performed by using FAST v8. Simulations are set up based on the LIFES50+ Site B (medium severity). A comparison is made to a similar study with a different platform (Olav Olsen semi-submersible) in order to observe if similar conclusions can be reached for the different floater types.