In design of offshore wind turbines, extreme wave conditions are of interest. Usually, the design wave condition is taken as the sea state corresponding to an annual exceedance probability of 2 × 10−2, i.e., a return period of 50 years. A possible location for a future wind farm, consisting of bottom fixed wind turbines, is the Doggerbank area. The water depth in this area varies from about 60 m in the north to about 20 m in the south. The hindcast database NORA10 provides sea state characteristics from 1957 to present over a domain covering Doggerbank. Regarding the deeper areas just north of Doggerbank, this hindcast model is found to be of good quality. Larger uncertainties are associated with the hindcast results as we approach shallower water further south. The purpose of the present study is to compare sea state evolution over Doggerbank as reflected by NORA10 with the results of the commonly used shallow water hindcast model SWAN. The adequacy of the default parameters of SWAN for reflecting changes in wave conditions over a sloping bottom is investigated by comparison with model test results. Extreme wave conditions for two locations 102.5 km apart in a north–south direction are established using NORA10. This is done using both, an all sea states approach and a peak over threshold (POT) approach. Assuming the extremes for the northern position to represent good estimates, the wave evolution southward is analyzed using SWAN. The extreme condition obtained from NORA10 in the northern position is used as input to SWAN and the results from the two hindcast models are compared in the southern position. SWAN seems to suggest a somewhat faster decay over Doggerbank compared to NORA10.

References

References
1.
Reistad
,
M.
,
Breivik
,
Ø.
,
Haakenstad
,
H.
,
Aarnes
,
O. J.
,
Furevik
,
B. R.
, and
Bidlot
,
J.-R.
,
2011
, “
A High-Resolution Hindcast of Wind and Waves for the North Sea, the Norwegian Sea, and the Barents Sea
,”
J. Geophys. Res.: Oceans
,
116
(
C5
), p.
C05019
.
2.
The Wamdi Group
,
1988
, “
The WAM Model—A Third Generation Ocean Wave Prediction Model
,”
J. Phys. Oceanogr.
,
18
(
12
), pp.
1775
1810
.
3.
Komen
,
G. J.
,
Cavaleri
,
L.
,
Donelan
,
M.
,
Hasselmann
,
K.
,
Hasselmann
,
S.
, and
Janssen
,
P. A. E. M.
,
1994
,
Dynamics and Modelling of Ocean Waves
,
Cambridge University Press, Cambridge Books Online
,
Cambridge, UK
.
4.
Günther
,
H.
,
Rosenthal
,
W.
,
Stawarz
,
M.
,
Carretero
,
J. C.
,
Gomez
,
M.
,
Lozano
,
I.
,
Serrano
,
O.
, and
Reistad
,
M.
,
1988
, “
The Wave Climate of the Northeast Atlantic Over the Period 1955–1994: The Wasa Wave Hindcast
,”
Global Atmos. Ocean Syst.
,
6
, pp.
121
163
.
5.
Bruserud
,
K.
,
Nygaard
,
E.
, and
Johannessen
,
K.
,
2010
, “
Wave and Wind Calibration Atlas for the Western Europe
,” Statoil Document No. MMG-MGE-RA 00017, Revision 2.
6.
Mathiesen
,
M.
,
2010
, “
Wam10 Data Archive Ű Use of Wind and Wave Data
,” Statoil Memo, Revision 2.
7.
DNV
,
2013
,
Design of Offshore Wind Turbine Structures
, Document No. DNV-OS-J101.
8.
DNV
,
2010
,
Environmental Conditions and Environmental Loads
, Document No. DNV-RP-C205.
9.
Haver
,
S.
, and
Nyhus
,
K.
,
1986
, “
A Wave Climate Description for Long Term Response Calculations
,”
Fifth International Offshore Mechanics and Arctic Engineering Symposium
, Vol.
4
, pp.
27
34
.
10.
Bury
,
K.
,
1975
,
Statistical Models in Applied Science
(Wiley Series in Probability and Mathematical Statistics),
Wiley
,
New York
.
11.
Holthuijsen
,
L. H.
,
2007
,
Waves in Oceanic and Coastal Waters
,
Cambridge University Press, Cambridge Books Online
,
Cambridge, UK
.
12.
SWAN
,
2013
, “
SWAN User Manual for SWAN Cycle III Version 40.91ABC
.”
13.
SWAN
,
2013
, “
SWAN Scientific and Technical Documentation for SWAN Cycle III Version 40.91ABC
.”
14.
Svangstu
,
E.
,
2011
, “
An Investigation of Wave Conditions and Wave Induced Loads for Design of Wind Turbine Foundations at 15–40 m Depth
,”
M.S. thesis
, Norwegian University of Science and Technology, Trondheim, Norway.
15.
Zijlema
,
M.
,
van Vledder
,
G.
, and
Holthuijsen
,
L.
,
2012
, “
Bottom Friction and Wind Drag for Wave Models
,”
Coastal Eng.
,
65
, pp.
19
26
.
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