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Special Section Articles

Dynamic Analysis of a Floating Offshore Wind Turbine Under Extreme Environmental Conditions

[+] Author and Article Information
Tomoaki Utsunomiya

Department of Civil and Earth
Resources Engineering,
Kyoto University,
Nishikyo-ku,
Kyoto 615-8540, Japan
e-mail: utsunomiya.tomoaki.4m@kyoto-u.ac.jp

Shigeo Yoshida

Hitachi, Ltd. Power Systems Company,
Shirogane-cho 1-1-1,
Hitachi, Ibaraki 317-0056, Japan

Hiroshi Ookubo

Nippon Steel & Sumikin Engineering Co., Ltd.,
Shintomi 20-1,
Futtsu, Chiba 293-0011, Japan

Iku Sato

Toda Corporation,
Kyobashi 1-7-1,
Chuo-ku, Tokyo 104-8388, Japan

Shigesuke Ishida

National Maritime Research Institute,
Shinkawa 6-38-1,
Mitaka, Tokyo 181-0004, Japan

Contributed by the Ocean, Offshore, and Arctic Engineering Division of ASME for publication in the JOURNAL OF OFFSHORE MECHANICS AND ARCTIC ENGINEERING. Manuscript received December 16, 2012; final manuscript received October 2, 2013; published online March 24, 2014. Assoc. Editor: Krish Thiagarajan.

J. Offshore Mech. Arct. Eng 136(2), 020904 (Mar 24, 2014) (11 pages) Paper No: OMAE-12-1110; doi: 10.1115/1.4025872 History: Received December 16, 2012; Revised October 02, 2013

This paper is concerned with the development of a floating offshore wind turbine (FOWT) utilizing spar-type floating foundation. In order to design such a structure, it is essential to evaluate the dynamic response under extreme environmental conditions. In this study; therefore, a dynamic analysis tool has been developed. The dynamic analysis tool consists of a multibody dynamics solver (MSC.Adams), aerodynamic force evaluation library (NREL/AeroDyn), hydrodynamic force evaluation library (in-house program named SparDyn), and mooring force evaluation library (in-house program named Moorsys). In this paper, some details of the developed dynamic analysis tool are given. In order to validate the program, comparison with the experimental results, where the wind, current, and wave are applied simultaneously, has been made. In this paper, only parked conditions are considered. The comparison shows that the principal behavior of the floating offshore wind turbine with spar platform has been captured by the developed program. However, when vortex-induced motion (VIM) occurs, the current loads and cross-flow responses (sway and roll) are underestimated by the simulation since the simulation code does not account for the effect of VIM.

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References

Figures

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Fig. 1

Aero-hydro-servo-mooring dynamics integrated dynamic analysis tool

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Fig. 2

Floating offshore wind turbine model (in m)

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Fig. 3

Experimental wind turbine model and the tower base coordinate system (scale = 1/34.5; R = 320 mm, L = 51 mm, a = 6 deg, tower diameter = 50 mm, hub height = 501 mm). The graph shows the plan shape of a blade (LE: leading edge (mm), TE: trailing edge (mm)).

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Fig. 4

Comparison of wind-induced forces/moments at the tower base (roll = 0 deg, pitch = 0 deg; marks: experiments; lines: simulations)

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Fig. 5

Comparison of wind-induced forces/moments at the tower base (roll = − 30 deg, pitch = 0 deg; marks: experiments; lines: simulations)

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Fig. 6

Comparison of wind-induced forces/moments at the tower base (roll = 30 deg, pitch = 0 deg; marks: experiments; lines: simulations)

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Fig. 7

Comparison of wind-induced forces/moments at the tower base (roll = 0 deg, pitch = −30 deg; marks: experiments; lines: simulations)

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Fig. 8

Comparison of wind-induced forces/moments at the tower base (roll = 0 deg, pitch = 30 deg; marks: experiments; lines: simulations)

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Fig. 9

Comparison of free yaw motions (upper: without fins; lower: with fins)

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Fig. 10

Definition of cases for wind, wave, and current directions

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Fig. 11

Wind speed in time series and in power spectrum (Cal: used in simulation as input; Exp: measured in experiment)

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Fig. 12

Current speed in time series and in power spectrum (low-pass filtered at 0.04 Hz; Cal: used in simulation as input; Exp: measured in experiment)

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Fig. 13

Comparison of wave power spectra (Cal: used in simulation as input; Exp: measured in experiment)

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Fig. 14

Comparison of COG motions in time series for case 1

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Fig. 15

Comparison of horizontal mooring-line forces in time series for case 1 (low-pass filtered at 0.33 Hz for experimental data)

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Fig. 16

Comparison of COG motions in power spectra for case 1

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Fig. 17

Comparison of horizontal mooring line forces in power spectra for case 1 (low-pass filtered at 0.33 Hz for experimental data)

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Fig. 18

Comparison of COG motions in time series for case 2

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Fig. 19

Comparison of horizontal mooring-line forces in time series for case 2 (low-pass filtered at 0.33 Hz for experimental data)

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Fig. 20

Comparison of COG motions in power spectra for case 2

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Fig. 21

Comparison of horizontal mooring-line forces in power spectra for case 2 (low-pass filtered at 0.33 Hz for experimental data)

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Fig. 22

Comparison of COG motions in time series for case 3

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Fig. 23

Comparison of horizontal mooring-line forces in time series for case 3 (low-pass filtered at 0.33 Hz for experimental data)

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Fig. 24

Comparison of COG motions in power spectra for case 3

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Fig. 25

Comparison of horizontal mooring-line forces in power spectra for case 3 (low-pass filtered at 0.33 Hz for experimental data)

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Fig. 26

COG motions in time series at a constant towing speed (a) Sway (U = 0.19 m/s), (b) Sway (U = 0.56 m/s), and (c) Roll (U = 0.19 m/s) (d) Roll (U = 0.56 m/s)

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Fig. 27

Comparison of cross-flow VIM response for sway with DNV-RP-C205

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Fig. 28

Comparison of cross-flow VIM response for roll with DNV-RP-C205. ACF is calculated by ACF = CG*AROLL where CG = 22.23 m ( = the distance from sea-surface to the center of gravity)

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