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Keywords:

  • floating wind turbine;
  • vortex ring state;
  • unsteady aerodynamics;
  • reduced frequency;
  • offshore

ABSTRACT

Large-scale offshore floating wind turbines were first proposed in 1972 by Prof. William E. Heronemus at the University of Massachusetts. Since then, very little progress has been made in the deployment of these systems despite the significant advantages afforded by floating wind turbines, namely access to superior wind resources and increased placement flexibility. Aside from the large capital costs associated with construction, one of the most significant challenges facing offshore floating wind turbines is a limited simulation and load estimation capability. Many wind turbine aerodynamic analysis methods rely on assumptions that may not be applicable to the highly dynamic environment in which floating wind turbines are expected to operate. This study characterizes the unique operating conditions that make aerodynamic analysis of offshore floating wind turbines a challenge. Conditions that may result in unsteady flow are identified, and a method to identify aerodynamically relevant platform modes is presented. Operating conditions that may result in a breakdown of the momentum balance equations are also identified for different platform configurations. It is shown that offshore floating wind turbines are subjected to significant aerodynamic unsteadiness fixed-bottom offshore turbines. Aerodynamic analysis of offshore floating wind turbines may require the use of higher-fidelity ‘engineering-level’ models than commonly in use today. Copyright © 2012 John Wiley & Sons, Ltd.