Wave-Structure Interaction of Floating Wind Turbines - A Combined Numerical and Experimental Investigation

University Of California-San Diego, La Jolla CA

Investigators

Abstract

0967023 Zhu Floating wind turbines are novel renewable energy devices designed to operate in deep waters (>60 m), where most of the offshore wind energy resource is found. These floating turbines are structurally different from other existing offshore systems, and their structural stability in offshore conditions has not been extensively tested. Intellectual Merit This interdisciplinary research effort will make use of an experimental facility for earthquake engineering and state-of-the-art computational methods to study the dynamic structural responses of floating wind turbines in ocean waves. Two models, a frequency-domain model and a nonlinear time-domain model, will be developed to study the fluid-structure interaction problem. For simulations of wave-body interaction, the first model uses a linear boundary element model, while the second model applies a fully-nonlinear mixed-Eularian-Lagragian method. Both models include a comprehensive, fully-nonlinear dynamic model of the mooring system and a FEM model of the structural responses. The two-model approach enables the study of both long-term responses of the system (e.g. for fatigue studies) and transient response due to large waves (e.g. rogue waves). The research plan will focus on three areas: long-term structural response in wave fields, wave-structure resonances, and responses to large waves. For the model verification studies, full-scale shake table experiments will be carried out on a 65 kW system, and the recorded structural responses will be compared with model predictions. The models will then be used to predict the performance of a scaled-up 5 MW system. This research is potentially transformative because it will provide new tools to evaluate the feasibility of current designs for floating wind turbines. This research could also be used to guide the development of future deep-water offshore wind farms. Broader Impacts A unique aspect of this work is that it uses earthquake engineering tools, specifically the Large High-Performance Outdoor Shake Table at University of California - San Diego, to study offshore wind energy structures. In addition to training of undergraduate and graduate students directly involved in the research effort, learning materials based on their research will be incorporated into existing undergraduate and graduate structural and fluids mechanics courses. Other activities include using the Large High-Performance Outdoor Shake Table at University of California at San Diego as a demonstration to reach out to K-12 students from under-represented groups on topics related to renewable energy. Websites for this facility will be updated to include the floating wind turbine.