OpenFAST Modeling of the T-Omega Wind Floating Offshore Wind Turbine System

Lu Wang, Jason Jonkman, Jim Papadopoulos, Andrew Myers

Research output: NRELPresentation


To reduce the cost of offshore wind energy through a more efficient design of the floating support structure, T-Omega Wind developed a novel lightweight and shallow-draft platform concept that aims to achieve a wave-following behavior without resonance amplification. The rotor and generator are carried by four tower legs with each leg supported by a shallow-draft float at the base. In preparation for a more detailed analysis, a coupled aero-hydro-elastic model of the proposed concept is developed in OpenFAST. The detailed modeling approach is presented, including a novel application of the SubDyn substructure dynamics module of OpenFAST to approximate the loads on the axle tube at the tower top from the rotor hub bearings. Preliminary results obtained with the OpenFAST model by rigidifying the substructure and blades indicate that the original sizing of the design can lead to large hub acceleration in the axial/surge and pitch directions due to platform-pitch motion. The high axial acceleration also potentially leads to large bending moments in the four tower legs. To address these issues, an updated design is developed with, among other changes, increased float spacing at the tower base and improved shear-transmitting geometry of the tower legs. The new design suggests significantly reduced extreme hub accelerations under the same conditions even with structural flexibility and will be further analyzed in the future through full aero-hydro-servo-elastic simulations.
Original languageAmerican English
Number of pages18
StatePublished - 2023

Publication series

NamePresented at the ASME 2023 5th International Offshore Wind Technical Conference, 18-19 December 2023, Exeter, United Kingdom

NREL Publication Number

  • NREL/PR-5000-87681


  • FOWT
  • hydroelasticity
  • lightweight
  • OpenFAST
  • shallow draft


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