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.

References

References
1.
Ormberg
,
H.
,
Fylling
,
I.
,
Larsen
,
K.
, and
Sødahl
,
N.
,
1997
, “
Coupled Analysis of Vessel Motions and Mooring and Riser System Dynamics
,”
Offshore Mechanics and Arctic Engineering Conference
(OMAE), Yokohama, Japan, Apr. 13–17, pp.
91
100
.
2.
Moriarty
,
P. J.
, and
Hansen
,
A. C.
,
2005
, “
AeroDyn Theory Manual
,” National Renewable Energy Laboratory, Golden, CO,
Technical Report No. NREL/TP-500-36881
.
3.
Ormberg
,
H.
, and
Bachynski
,
E. E.
,
2012
, “
Global Analysis of Floating Wind Turbines: Code Development, Model Sensitivity and Benchmark Study
,”
22nd International Offshore and Polar Engineering Conference
, Rhodes, Greece, June 17–22, Vol.
1
, pp.
366
373
.
4.
Karunakaran
,
D.
,
Haver
,
S.
,
Bærheim
,
M.
, and
Spidsøe
,
N.
,
2001
, “
Dynamic Behaviour of the Kvitebjørn Jacket in the North Sea
,”
20th International Conference on Offshore Mechanics and Arctic Engineering
, Rio de Janeiro, Brazil, Paper No. OMAE01/OFT-1184.
5.
Vorpahl
,
F.
,
Kaufer
,
D.
, and
Popko
,
W.
,
2011
, “
Description of a Basic Model of the “UpWind Reference Jacket” for Code Comparison in the OC4 Project Under IEA Wind Annex 30
,” Technical Report, Fraunhofer Institute for Wind Energy and Energy System Technology
IWES
, Bremerhaven, Germany.
6.
Jonkman
,
J.
,
Butterfield
,
S.
,
Musial
,
W.
, and
Scott
,
G.
,
2009
, “
Definition of a 5-MW Reference Wind Turbine for Offshore System Development
,” National Renewable Energy Laboratory, Golden, CO,
Technical Report No. NREL/TP-500-38060
.
7.
Long
,
H.
,
Moe
,
G.
, and
Fischer
,
T.
,
2012
, “
Lattice Towers for Bottom-Fixed Offshore Wind Turbines in the Ultimate Limit State: Variation of Some Geometric Parameters
,”
ASME J. Offshore Mech. Arct. Eng.
,
134
(
2
), p.
021202
.
8.
Vemula
,
N. K.
,
DeVries
,
W.
,
Fischer
,
T.
, and
Schmidt
,
B.
,
2010
, “
Design Solution for the UpWind Reference Offshore Support Structure
,” Technical Report, Upwind Deliverable D4.2.6 (WP4: Offshore Foundations and Support Structures), Rambøll Wind Energy, Esbjerg, Denmark.
9.
Long
,
H.
,
2013
, personal communication by email.
10.
Ong
,
M. C.
,
Li
,
H.
,
Leira
,
B. J.
, and
Myrhaug
,
D.
,
2013
, “
Dynamic Analysis of Offshore Monopile Wind Turbine Including the Effects of Wind-Wave Loading and Soil Properties
,”
32nd International Conference on Ocean
, Offshore and Arctic Engineering, Nantes, France,
Paper No. OMAE2013-10527
.
11.
Salzmann
,
D. J. C.
, and
van der Tempel
,
J.
,
2005
, “
Aerodynamic Damping in the Design of Support Structures for Offshore Wind Turbines
,”
Offshore Wind Energy Conference
, Copenhagen, Denmark, pp. 1–9.
12.
Bachynski
,
E. E.
,
2014
, “
Design and Dynamic Analysis of Tension Leg Platform Wind Turbines
,”
Ph.D. thesis
, Norwegian University of Science and Technology, Trondheim, Norway.
13.
Kvittem
,
M. I.
,
2014
, “
Modelling and Response Analysis for Fatigue Design of a Semi-Submersible Wind Turbine
,”
Ph.D. thesis
, Norwegian University of Science and Technology, Trondheim, Norway.
14.
Popko
,
W.
,
Vorpahl
,
F.
,
Zuga
,
A.
,
Kohlmeier
,
M.
,
Jonkman
,
J.
,
Robertson
,
A.
,
Larsen
,
T. J.
, and
Yde
,
A.
,
2012
, “
Offshore Code Comparison Collaboration Continuation (OC4), Phase I: Results of Coupled Simulations of an Offshore Wind Turbine With Jacket Support Structure
,”
22nd International Society of Offshore and Polar Engineers Conference
, Rhodes, Greece, June 17–22, Vol.
1
, pp.
337
348
.
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