jjonkman
commented
1 year ago Dear @CharlesYouOUC,
I'm not an author of the OTC paper you reference, but I'm not surprised that a model-scale physical model will have a slightly different tower natural frequency than the full-scale numerical model given the difficulties scaling everything to model scale (especially the rotor and nacelle).
The data from the IEA Wind Task 30 OC4 Phase II project is archived in the following Google drive: https://drive.google.com/drive/folders/0B0KGNSHvXXgCVTZpU2thUDQtNnM?resourcekey=0-p6CkChh-R5Bwd-rSYU1ycg&usp=drive_link.
Best regards,
Dear Dr. Jonkman, Recently I have studied the reference below about the natural frequencies of the NREL 5MW-OC4 DeepCwind SemiSubmersible wind turbine. I have noticed a difference in the description of the tower frequency of the OC4 semi-submersible wind turbine in the two documents. Ref[1] Fig3 shows the first order natural frequency of the tower in the fore and aft direction to be 0.41 Hz, while ref[2] Table6 shows this frequency to be 0.35 Hz. I do not understand the reason for the difference in the natural frequency of the tower. Also, I would like to know how to obtain the specific data about Fig3 in ref[1]. [1] Offshore Code Comparison Collaboration Continuation Within IEA Wind Task 30: Phase II Results Regarding a Floating Semisubmersible Wind System. “https://doi.org/10.1115/OMAE2014-24040” [2] Model Test for Three Floating Wind Turbine Concepts. “OTC 23470” “https://doi.org/10.4043/23470-MS”