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Research Papers: Ocean Renewable Energy

Dynamic Responses of Jacket-Type Offshore Wind Turbines Using Decoupled and Coupled Models

[+] Author and Article Information
Muk Chen Ong

Professor
Department of Mechanical and Structural,
Engineering and Materials Science,
University of Stavanger (UiS),
Stavanger 4036, Norway
e-mail: muk.c.ong@uis.no

Erin E. Bachynski

Associate Professor
Department of Marine Technology,
Norwegian University of Science and
Technology (NTNU),
Trondheim 7491, Norway
e-mail: erin.bachynski@ntnu.no

Ole David Økland

Norwegian Marine Technology
Research Institute (MARINTEK),
Trondheim 7052, Norway
e-mail: Ole.Okland@marintek.sintef.no

1Corresponding author.

Contributed by the Ocean, Offshore, and Arctic Engineering Division of ASME for publication in the JOURNAL OF OFFSHORE MECHANICS AND ARCTIC ENGINEERING. Manuscript received September 9, 2016; final manuscript received January 7, 2017; published online May 5, 2017. Assoc. Editor: Yi-Hsiang Yu.

J. Offshore Mech. Arct. Eng 139(4), 041901 (May 05, 2017) (8 pages) Paper No: OMAE-16-1111; doi: 10.1115/1.4035772 History: Received September 09, 2016; Revised January 07, 2017

This paper presents numerical studies of the dynamic responses of two jacket-type offshore wind turbines (OWTs) using both decoupled and coupled models. The investigated structures are the OC4 (Offshore Code Comparison Collaboration Continuation) jacket foundation and a full-lattice support structure presented by Long et al., 2012, “Lattice Towers for Bottom-Fixed Offshore Wind Turbines in the Ultimate Limit State: Variation of Some Geo metric Parameters,” ASME J. Offshore Mech. Arct. Eng., 134(2), p. 021202. Both structures support the NREL 5-MW wind turbine. Different operational wind and wave loadings at an offshore site with relatively high soil stiffness are investigated. In the decoupled (hydroelastic) model, the thrust and torque from an isolated rotor model were used as wind loads on the decoupled model together with a linear aerodynamic damper. The coupled model is a hydro-servo-aero-elastic representation of the system. The objective of this study is to evaluate the applicability of the computationally efficient linear decoupled model by comparing with the results obtained from the nonlinear coupled model. Good agreement was obtained in the eigen-frequency analysis, decay tests, and wave-only simulations. It was also found that, by applying the thrust force from an isolated rotor model in combination with linear damping, reasonable agreement could be obtained between the decoupled and coupled models in combined wind and wave simulations.

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References

Figures

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Fig. 1

OC4 jacket OWT, modeled in SIMA

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Fig. 2

Full-lattice OWT, modeled in SIMA

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Fig. 3

Global coordinate system at the tower top

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Fig. 4

Configuration of the decoupling method

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Fig. 5

Decay test with OC4 jacket OWT. Tower top fore-aft displacement is shown.

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Fig. 6

Time series of the axial force in element 1 of the OC4 jacket for EC4, wave-only

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Fig. 7

Spectrum of the axial force in element 1 of the OC4 jacket for EC4, wave-only

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Fig. 8

Time series of the axial force in element 1 of the full-lattice jacket for EC4, wave-only

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Fig. 9

Spectrum of the axial force in element 1 of the full-lattice jacket for EC4, wave-only

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Fig. 10

Time-series plots of the displacement of the tower top in x-direction, the axial force in element 1, and the tower base moment for the OC4 jacket in EC2, combined wind and waves

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Fig. 11

Spectra of the displacement of the tower top in x-direction, the axial force in element 1, and the tower base moment for the OC4 jacket in EC2, combined wind and waves

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Fig. 12

Spectra of the displacement of the tower top in x-direction, the axial force in element 1, and the tower base moment for the OC4 jacket in EC4, combined wind and waves

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Fig. 13

Spectra of the tower top displacement and the axial forces in lines 1 and 2, lattice, EC2, combined wind and wave

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Fig. 14

Spectra of the tower top displacement and the axial forces in lines 1 and 2, lattice, EC4, combined wind and wave

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