The current paper deals with a study of a semisubmersible wind turbine (WT), where short-term tower base bending moments and tower fatigue damage were estimated by a frequency domain (FD) method. Both a rigid structure assumption and a generalized degree-of-freedom (DOF) model for including the first flexible mode of the turbine tower were investigated. First, response to wind and wave loads was considered separately, then superposition was used to find the response to combined wind and wave loading. The bending moments and fatigue damage obtained by these methods were compared to results from a fully coupled, nonlinear time domain (TD) analysis. In this study a three column, catenary moored semisubmersible with the NREL 5 MW turbine mounted on one of the columns was modeled. The model was inspired by the WindFloat concept. The TD simulation tool used was Simo-Riflex-AeroDyn from Marintek and CeSOS. The FD method gave a good representation of the tower base bending moment histories for wave-only analyses, for the moderate sea states considered in these analyses. With the assumption that the structure is completely rigid, bending moments were underestimated, but including excitation of the elastic tower and blades, improved the results. The wind-induced low-frequency bending moments were not captured very well, which presumably comes from a combination of nonlinear effects being lost in the linearization of the thrust force and that the aerodynamic damping model was derived for a fixed turbine. Nevertheless, standard deviations of the bending moments were still reasonable. The FD model captured the combined wind and wave analyses quite well when a generalized coordinates model for wind excitation of the first bending mode of the turbine was included. The FD fatigue damage predictions were underestimated by 0–60%, corresponding to discrepancies in standard deviations of stress in the order of 0–20%.

References

References
1.
Det Norske Veritas,
2012
, “
Column-Stabilised Units
,” p.
20
, No. DNV-RP-C103.
2.
Burton
,
T.
,
Jenkins
,
N.
,
Sharpe
,
D.
, and
Bossanyi
,
E.
,
2011
,
Wind Energy Handbook, Wiley
,
West Sussex
,
UK
, Chap. 5.
3.
Sørensen
,
P.
,
Larsen
,
G. C.
, and
Christensen
,
C. J.
,
1995
, “
A Complex Frequency Domain Model of Wind Turbine Structures
,”
ASME J. Sol. Energy Eng.
,
117
(
4
), pp.
311
317
.10.1115/1.2847866
4.
Van Der Tempel
,
J.
,
2006
, “
Design of Support Structures for Offshore Wind Turbines
,” Ph.D. thesis, Technisce Universiteit Delft, Delft, The Netherlands.
5.
Bachynski
,
E. E.
, and
Moan
,
T.
,
2012
, “
Linear and Nonlinear Analysis of Tension Leg Platform Wind Turbines
,”
Proceedings of the 22nd International Ocean and Polar Engineering Conference
, Rhodes, Greece, June 17–22, Paper No. 2012-TPC-629, pp.
240
248
.
6.
Wayman
,
E. N.
,
Sclavounos
,
P. D.
,
Butterfield
,
S.
,
Jonkman
,
J.
, and
Musial
,
W.
,
2006
, “
Coupled Dynamic Modeling of Floating Wind Turbine Systems
,”
Offshore Technology Conference
, Houston, TX, May 1–4, Paper No. OTC-18287-MS, Vol.
139
.
7.
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, Chap. 5.
8.
Philippe
,
M.
,
Babarit
,
A.
, and
Ferrant
,
P.
,
2011
, “
Comparison of Time and Frequency Domain Simulations of an Offshore Floating Wind Turbine
,”
ASME 30th International Conference on Ocean, Offshore and Arctic Engineering
,
Rotterdam, The Netherlands
, June 19–24,
ASME
Paper No. OMAE2011-49722.10.1115/OMAE2011-49722
9.
Bulder
,
B. H.
,
van Hees
,
M. T.
,
Henderson
,
A.
,
Huijsmans
,
R. H. M.
,
Pierik
,
J. T. G.
,
Snijders
,
E. J. B.
,
Wijnants
,
G. H.
, and
Wolf
,
M. J.
,
2002
, “
Study to Feasibility of and Boundary Conditions for Floating Offshore Wind Turbines
,” ECN, MARIN, Lagerway the Windmaster, TNO, TUD, Technical Report No. 2002-CMC-R43.
10.
Vijfhuizen
,
W. J. M.
,
2006
, “
Design of a Wind and Wave Power Barge
,” M.S. thesis, Department of Naval Architecture and Mechanical Engineering, Universities of Glasgow and Strathclyde, Scotland.
11.
Lee
,
K. H.
,
2005
, “
Responses of Floating Wind Turbines to Wind and Wave Excitation
,” Ph.D. thesis, Massachusetts Institute of Technology, Cambridge, MA.
12.
Bachynski
,
E. E.
,
Kvittem
,
M. I.
,
Luan
,
C.
, and
Moan
,
T.
,
2013
, “
Wind-Wave Misalignment Effects on Floating Wind Turbines
,”
ASME J. Offshore Mech. Arct. Eng.
,
136
(
4
), p.
041902
.10.1115/1.4028028
13.
Kvittem
,
M. I.
, and
Moan
,
T.
,
2013
, “
Time Domain Analysis Procedures for Fatigue Assessment of a Semi-Submersible Wind Turbine
,” (submitted).
14.
Naess
,
A.
, and
Moan
,
T.
,
2013
,
Stochastic Dynamics of Marine Structures
,
Cambridge University
,
New York
, Chap. 14.
15.
Langen
,
I.
, and
Sigbjörnsson
,
R.
,
1979
,
Dynamisk Analyse av Konstruksjoner: Dynamic Analysis of Structures
,
Tapir, Trondheim, Norway
, Chap. 9.
16.
Kvittem
,
M. I.
,
Moan
,
T.
,
Gao
,
Z.
, and
Luan
,
C.
,
2011
, “
Short-Term Fatigue Analysis of Semi-Submersible Wind Turbine Tower
,”
ASME 30th International Conference on Ocean, Offshore and Arctic Engineering
, Rotterdam, The Netherlands, June 19–24,
ASME
Paper No. OMAE2011-50092.10.1115/OMAE2011-50092
17.
Clough
,
R. W.
, and
Penzien
,
J.
,
1993
,
Dynamics of Structures
,
McGraw-Hill
,
New York
, Chap. 8.
18.
Van Rossum
,
G.
, and
Drake
,
F. L.
, Jr.
,
1995
,
Python Reference Manual
,
Centrum voor Wiskunde en Informatica
,
Amsterdam, The Netherlands
.
19.
Strømmen
,
E. N.
,
2010
,
Theory of Bridge Aerodynamics
,
Springer
,
Berlin, Germany
.
20.
Jonkman
,
J.
,
Butterfield
,
S.
,
Musial
,
W.
, and
Scott
,
G.
,
2009
, “
Definition of a 5-MW Reference Wind Turbine for Offshore System Development
,” NREL, Technical Report No. NREL/TP-500-38060.
21.
Jonkman
,
J.
,
2010
, “
Definition of the Floating System for Phase IV of OC3
,” NREL, Technical Report No. NREL/TP-500-47535.
22.
Roddier
,
D.
,
Peiffer
,
A.
,
Aubault
,
A.
, and
Weinstein
,
J.
,
2011
, “
A Generic 5MW WindFloat for Numerical Tool Validation and Comparison Against a Generic Spar
,”
ASME 30th International Conference on Ocean Offshore and Arctic Engineering
, Rotterdam, The Netherlands, June 19–24,
ASME
Paper No. OMAE2011-50278.
23.
Det Norske Veritas,
2008
, SESAM User Manual Wadam.
24.
Kvittem
,
M. I.
, and
Moan
,
T.
,
2012
, “
Effect of Mooring Line Modeling on Motions and Structural Fatigue Damage for a Semisubmersible Wind Turbine
,”
Proceedings of the 22nd International Ocean and Polar Engineering Conference
, Rhodes, Greece, June 17–22, pp.
273
278
.
25.
Ormberg
,
H.
, and
Bachynski
,
E. E.
,
2012
, “
Global Analysis of Floating Wind Turbines: Code Development, Model Sensitivity and Benchmark Study
,”
Proceedings of the 22nd International Ocean and Polar Engineering Conference
, Rhodes, Greece, June 17–22, pp.
366
373
.
26.
Kvittem
,
M. I.
,
Bachynski
,
E. E.
, and
Moan
,
T.
,
2012
, “
Effects of Hydrodynamic Modeling in Fully Coupled Simulations of a Semi-Submersible Wind Turbine
,”
Energy Procedia
,
24
, pp.
351
362
.10.1016/j.egypro.2012.06.118
27.
Det Norske Veritas,
2010
, “
Fatigue Design of Offshore Steel Structures
,” No. DNV-RP-C203.
28.
Li
,
L.
,
Gao
,
Z.
, and
Moan
,
T.
,
2013
, “
Joint Environmental Data at Five European Offshore Sites for Design of Combined Wind and Wave Energy Devices
,”
ASME 32nd International Conference on Ocean, Offshore and Arctic Engineering
,
Nantes, France
, June 9–14,
ASME
Paper No. OMAE2013-10156.10.1115/OMAE2013-10156
29.
Jonkman
,
B. J.
,
2009
, TurbSim User's Guide.
30.
International Electrotechnical Commission
,
2005
, “
Wind Turbines—Part 1: Wind Turbines, Design Requirements
,” No. IEC61400-1.
31.
International Electrotechnical Commission
,
2009
, “
Wind Turbines—Part 3: Design Requirements for Offshore Wind Turbines
,” No. IEC61400-3.
You do not currently have access to this content.