Aeroelastic and Hydrodynamic Loads and Structural Dynamics of Large MW-Scale Offshore Wind Turbines in Shallow-water GOM

Offshore wind energy production has been expanding rapidly worldwide in the past decade owing to the vast wind resources offshore. Increasingly large MW-scale wind turbines are used to improve their costs and efficiency. While in regardless of the high potential in offshore wind resources, offshore wind turbines are not currently in use to generate electricity in any U.S. water. In the study, an investigation is conducted on the feasibility of using a large MW-scale (13.2-MW) wind turbine with a fixed-bottom mono-tower support structure in U.S. hurricane-prone western Gulf of Mexico (GOM) shallow water, with focus on the modeling and structural dynamics of the offshore wind turbine (OWT). In order to evaluate the feasibility, design of the turbine components, structure integrity, turbine structural dynamics and load analysis need to be carried out. The wind turbine site and metocean conditions are first specified with particular interest in extreme condition in the GOM shallow water. A mono-tower support structure is properly sized for the 13.2-MW wind turbine to sustain a 100-year return hurricane in the site, with which the entire offshore wind turbine is constructed in several established computational mechanics tools. Wind, wave and current loads on, and dynamic responses of the 13.2-MW OWT in normal operation and in the 100-year return hurricane are determined using the computational tools. Effects of turbine operation on dynamic load and turbine responses are evaluated. Important resonance issue owing to the interaction of the wind turbine components and excitation from environment is clarified. Mono-pile length below the mud line of the 13.2-MW OWT mono-tower support structure is properly determined to investigate the important effects of pile-soil interaction on the tower and rotor dynamics as well as rotor performance. In addition, the sizing method for the 13.2-MW turbine mono-tower is generalized to design tower structures for other large offshore wind turbines with power ratings up to 20 MW. 100-year return hurricane loads are evaluated for the large OWTs in the western GOM shallow water. Feasibility of operating large MW-scale wind turbines in U.S. hurricane-prone western Gulf of Mexico shallow water is clarified.