Date of Award

Fall 12-15-2023

Level of Access Assigned by Author

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)


Mechanical Engineering


Andrew J. Goupee

Second Committee Member

Richard W. Kimball

Third Committee Member

Anthony M. Viselli

Additional Committee Members

Amrit S. Verma

Todd Griffith


This thesis presents results from the Floating Offshore-wind and Controls Advanced Laboratory (FOCAL) Experiment which performed 1:70-scale model testing of a 15 mega-watt floating offshore wind turbine (FOWT) at the University of Maine’s Alfond Wind/Wave Ocean Engineering Laboratory (W2). The experimental campaigns supported the application of controls co-design to FOWTs by incorporating real-time wind turbine control and hull mounted tuned-mass damper (TMD) elements. A performance-matched scaling strategy was proposed and analysis in OpenFAST performed to design the scale models, including integration of the Reference OpenSource Controller (ROSCO) and modeling of the TMDs in the hull. Four test campaigns were conducted, first characterizing the performance of the turbine and hull separately in wind and wave only environments, respectively. The combined system was then characterized in wind and wave environments, investigating effects of control strategies such as thrust peak shaving, floating feedback, and different TMD frequencies. Data were collected and used to validate OpenFAST models developed by the FOCAL team as well as mid- and high-fidelity tools developed by other ATLANTIS teams.

Key outcomes consisted of demonstrating the ability to tune ROSCO and control the scale model turbine and investigating the impacts of ROSCO on system behavior, including attenuation of platform pitch motion and tower base bending moments in response to the thrust peak shaving and floating feedback control. The TMDs demonstrated effective attenuation of platform pitch and tower bending moments at their respective resonant frequencies, as well as synergistic performance when combined with ROSCO’s floating feedback control. These findings identified opportunities for further optimization of FOWT systems through controls co-design and areas of future work to advance ROSCO and scale model testing of FOWTs with controls. Three datasets were generated and uploaded to the Atmosphere to Electrons portal including time history data, technical reports describing the experimental setup and test articles, and numerical models in Bladed and OpenFAST. Ten publications from the FOCAL team describe the design of the scale model, results of the numerical model validation, and discussion of the experimental results including the effects of ROSCO and TMDs on the performance of the floating wind turbine system.

PhD Thesis - Supplemental Materials.docx (13 kB)
Listing of supplemental materials/datasets and references

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