Volume 3, issue 2 | Copyright
Wind Energ. Sci., 3, 693-712, 2018
https://doi.org/10.5194/wes-3-693-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research articles 16 Oct 2018

Research articles | 16 Oct 2018

An efficient frequency-domain model for quick load analysis of floating offshore wind turbines

Antonio Pegalajar-Jurado, Michael Borg, and Henrik Bredmose Antonio Pegalajar-Jurado et al.
  • Department of Wind Energy, Technical University of Denmark, Nils Koppels Allé 403, 2800 Kongens Lyngby, Denmark

Abstract. A model for Quick Load Analysis of Floating wind turbines (QuLAF) is presented and validated here. The model is a linear, frequency-domain, efficient tool with four planar degrees of freedom: floater surge, heave, pitch and first tower modal deflection. The model relies on state-of-the-art tools from which hydrodynamic, aerodynamic and mooring loads are extracted and cascaded into QuLAF. Hydrodynamic and aerodynamic loads are pre-computed in WAMIT and FAST, respectively, while the mooring system is linearized around the equilibrium position for each wind speed using MoorDyn. An approximate approach to viscous hydrodynamic damping is developed, and the aerodynamic damping is extracted from decay tests specific for each degree of freedom. Without any calibration, the model predicts the motions of the system in stochastic wind and waves with good accuracy when compared to FAST. The damage-equivalent bending moment at the tower base is estimated with errors between 0.2% and 11.3% for all the load cases considered. The largest errors are associated with the most severe wave climates for wave-only conditions and with turbine operation around rated wind speed for combined wind and waves. The computational speed of the model is between 1300 and 2700 times faster than real time.

Publications Copernicus
Download
Short summary
This paper presents a simplified numerical model to quickly predict motion and loads of floating offshore wind turbines. Hydrodynamic, aerodynamic and mooring loads are extracted from higher-fidelity numerical tools. Without calibration, the model can predict with good accuracy the motions of the system in real wind and wave conditions. Loads at the tower base are estimated with errors between 0.2 % and 11.3 %. The model can simulate between 1300 and 2700 times faster than real time.
This paper presents a simplified numerical model to quickly predict motion and loads of floating...
Citation
Share