The worldwide effort to design and commission floating offshore wind turbines (FOWT) is motivating the need for reliable numerical models that adequately represent their physical behavior under realistic sea states. However, properly representing the hydrodynamic quadratic damping for FOWT remains uncertain, because of its dependency on the choice of drag coefficients (dimensionless or not). It is hypothesized that the limited degree of freedom (DoF) drag coefficient formulation that uses only translational drag coefficients causes mischaracterization of the rotational DoF drag, leading to underestimation of FOWT global loads, such as tower base fore-aft shear. To address these hydrodynamic modeling uncertainties, different quadratic drag models implemented in the open-source mid-fidelity simulation tool, OpenFAST, were investigated and compared with the experimental data from the Offshore Code Comparison Collaboration, Continued, with Correlation (OC5) project. The tower base fore-aft shear and up-wave mooring line tension were compared under an irregular wave loading condition to demonstrate the effects of the different damping models. Two types of hydrodynamic quadratic drag formulations were considered: (1) member-based dimensionless drag coefficients applied only at the translational DoF (namely limited-DoF drag model) and (2) quadratic drag matrix model (in dimensional form). Based on the results, the former consistently underestimated the 95th percentile peak loads and spectral responses when compared to the OC5 experimental data. In contrast, the drag matrix models reduced errors in estimates of the tower base shear peak load by 7–10% compared to the limited-DoF drag model. The underestimation in the tower base fore-aft shear was thus inferred be related to mischaracterization of the rotational pitch drag and the heave motion/drag by the limited-DoF model.
Srinivas, Arjun, et al. "Impact of Limited Degree of Freedom Drag Coefficients on a Floating Offshore Wind Turbine Simulation." Journal of Marine Science and Engineering, vol. 11, no. 1, Jan. 2023. https://doi.org/10.3390/jmse11010139
Srinivas, Arjun, Robertson, Bryson, Gadasi, Jonah Benjamin, et al., "Impact of Limited Degree of Freedom Drag Coefficients on a Floating Offshore Wind Turbine Simulation," Journal of Marine Science and Engineering 11, no. 1 (2023), https://doi.org/10.3390/jmse11010139
@article{osti_1908303,
author = {Srinivas, Arjun and Robertson, Bryson and Gadasi, Jonah Benjamin and Simpson, Barbara Gwynne and Lomónaco, Pedro and Ilzarbe, Jesús María Blanco},
title = {Impact of Limited Degree of Freedom Drag Coefficients on a Floating Offshore Wind Turbine Simulation},
annote = {The worldwide effort to design and commission floating offshore wind turbines (FOWT) is motivating the need for reliable numerical models that adequately represent their physical behavior under realistic sea states. However, properly representing the hydrodynamic quadratic damping for FOWT remains uncertain, because of its dependency on the choice of drag coefficients (dimensionless or not). It is hypothesized that the limited degree of freedom (DoF) drag coefficient formulation that uses only translational drag coefficients causes mischaracterization of the rotational DoF drag, leading to underestimation of FOWT global loads, such as tower base fore-aft shear. To address these hydrodynamic modeling uncertainties, different quadratic drag models implemented in the open-source mid-fidelity simulation tool, OpenFAST, were investigated and compared with the experimental data from the Offshore Code Comparison Collaboration, Continued, with Correlation (OC5) project. The tower base fore-aft shear and up-wave mooring line tension were compared under an irregular wave loading condition to demonstrate the effects of the different damping models. Two types of hydrodynamic quadratic drag formulations were considered: (1) member-based dimensionless drag coefficients applied only at the translational DoF (namely limited-DoF drag model) and (2) quadratic drag matrix model (in dimensional form). Based on the results, the former consistently underestimated the 95th percentile peak loads and spectral responses when compared to the OC5 experimental data. In contrast, the drag matrix models reduced errors in estimates of the tower base shear peak load by 7–10% compared to the limited-DoF drag model. The underestimation in the tower base fore-aft shear was thus inferred be related to mischaracterization of the rotational pitch drag and the heave motion/drag by the limited-DoF model.},
doi = {10.3390/jmse11010139},
url = {https://www.osti.gov/biblio/1908303},
journal = {Journal of Marine Science and Engineering},
issn = {ISSN 2077-1312},
number = {1},
volume = {11},
place = {Switzerland},
publisher = {MDPI AG},
year = {2023},
month = {01}}
Fonseca, Nuno; Pessoa, Joa˜o; Guedes Soares, Carlos
Volume 6: Nick Newman Symposium on Marine Hydrodynamics; Yoshida and Maeda Special Symposium on Ocean Space Utilization; Special Symposium on Offshore Renewable Energyhttps://doi.org/10.1115/OMAE2008-57942