OC4-Jacket-OWT

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Zhou.Lin
Posts: 23
Joined: Tue May 15, 2018 6:00 am
Organization: Dalian University of Techology
Location: China

OC4-Jacket-OWT

Postby Zhou.Lin » Sun Nov 03, 2019 6:53 pm

Dear Jason,

I am simulating the offshore wind turbine of Oc4-jacket, I have some questions for the modal analysis, what is the second frequency of the whole system (including the substructure) of Oc4-jacket? If not, can bmodes calculate the second frequency of the whole system?

Looking forward to your reply and thank you for your kindness!

Best regards,
Zhou.Lin

Jason.Jonkman
Posts: 4338
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: OC4-Jacket-OWT

Postby Jason.Jonkman » Mon Nov 04, 2019 12:30 am

Dear Zhou.Lin,

According to the OC4 Phase I results (https://www.nrel.gov/docs/fy12osti/54124.pdf), the second global bending frequency of the tower + jacket of the OC4-jacket is around 1.2 Hz.

BModes can calculate tower natural frequencies, but the jacket must be simplified in BModes as a tower-base boundary condition involving 6x6 mass and stiffness matrices, which can be derived from the SubDyn summary file (hydro_M = MBBt, hydro_K = KBBt, mooring_K = 0).

I hope that helps.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov


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