Limited by layout space and manufacturing costs, wake interaction in offshore wind farms is inevitable and can have adverse effects on the performance of downstream wind turbines. To gain a better understanding of the wake interaction between Floating Offshore Wind Turbines (FOWTs), this paper conducts coupled aero-hydrodynamic simulations for two spar-type FOWTs under different layouts. The Unsteady Actuator Line Model (UALM) is used to analyze the unsteady aerodynamic loads of the wind turbine, while the hydrodynamic responses of the floating support platform are obtained using the Computational Fluid Dynamics (CFD) method. To predict the aero-hydrodynamic performance of the FOWT under combined wind and waves, an in-house CFD code developed at Shanghai Jiao Tong University (SJTU), called FOWT-UALM-SJTU solver, is utilized. First, grid convergence test and time step sensitivity study are performed to determine appropriate simulation parameters. Subsequently, numerical simulations of two FOWTs under tandem and offset layouts are conducted to investigate the influence of wake interaction on the performance of downstream FOWT. The dynamic responses of the FWOT, including aerodynamic loads, platform motions, and wake characteristics, are analyzed in detail. From the simulation results and discussions, several conclusions are drawn. Both platform motions and wake interaction contribute to an increased variation range of inflow wind speed experienced by the downstream FOWT, thereby exacerbating the instability of its aerodynamic loads. Under the tandem layout, the platform motions of the upstream FOWT and the downstream FOWT exhibit opposite effects on the aerodynamic loads of the downstream FOWT. Moreover, platform motions increase turbulence intensity in the wake region, accelerating wake velocity recovery and widening the wake width.

1.
Adaramola
,
M. S.
and
Krogstad
,
P.-Å.
, “
Experimental investigation of wake effects on wind turbine performance
,”
Renewable Energy
36
(
8
),
2078
2086
(
2011
).
2.
Archer
,
C. L.
,
Vasel-Be-Hagh
,
A.
,
Yan
,
C.
,
Wu
,
S.
,
Pan
,
Y.
,
Brodie
,
J. F.
, and
Maguire
,
A. E.
, “
Review and evaluation of wake loss models for wind energy applications
,”
Appl. Energy
226
,
1187
1207
(
2018
).
3.
Barthelmie
,
R. J.
,
Hansen
,
K.
,
Frandsen
,
S. T.
,
Rathmann
,
O.
,
Schepers
,
J. G.
, and
Schlez
,
W.
, “
Modelling and measuring flow and wind turbine wakes in large wind farms offshore
,”
Wind Energy
12
(
5
),
431
444
(
2009
).
4.
Chen
,
Z.
,
Wang
,
X.
,
Guo
,
Y.
, and
Kang
,
S.
, “
Numerical analysis of unsteady aerodynamic performance of floating offshore wind turbine under platform surge and pitch motions
,”
Renewable Energy
163
,
1849
1870
(
2021
).
5.
Cheng
,
P.
,
Huang
,
Y.
, and
Wan
,
D.
, “
A numerical model for fully coupled aero-hydrodynamic analysis of floating offshore wind turbine
,”
Ocean Eng.
173
,
183
196
(
2019
).
6.
Choi
,
N.
,
Nam
,
S.
, and
Jeong
,
J.
, “
CFD study on aerodynamic power output changes with inter-turbine spacing variation for a 6 MW offshore wind farm
,”
Energies
7
(
11
),
7483
7498
(
2014
).
7.
Choi
,
N. J.
,
Hyun
,
N. S.
, and
Hyun
,
J. J.
, “
Numerical study on the horizontal axis turbines arrangement in a wind farm: Effect of separation distance on the turbine aerodynamic power output
,”
J. Wind Eng. Ind. Aerodyn.
117
(
117
),
11
17
(
2013
).
8.
Dou
,
B.
,
Guala
,
M.
,
Lei
,
L.
, and
Zeng
,
P.
, “
Experimental investigation of the performance and wake effect of a small-scale wind turbine in a wind tunnel
,”
Energy
166
,
819
833
(
2019
).
9.
Fang
,
Y.
,
Duan
,
L.
,
Han
,
Z.
,
Zhao
,
Y.
, and
Yang
,
H.
, “
Numerical analysis of aerodynamic performance of a floating offshore wind turbine under pitch motion
,”
Energy
192
,
116621
(
2020
).
10.
Fei
,
Z.
,
Tengyuan
,
W.
,
Xiaoxia
,
G.
,
Haiying
,
S.
,
Hongxing
,
Y.
,
Zhonghe
,
H.
,
Wang
,
Y.
, and
Xiaoxun
,
Z.
, “
Experimental study on wake interactions and performance of the turbines with different rotor-diameters in adjacent area of large-scale wind farm
,”
Energy
199
,
117416
(
2020
).
11.
Gajardo
,
D.
,
Escauriaza
,
C.
, and
Ingram
,
D. M.
, “
Capturing the development and interactions of wakes in tidal turbine arrays using a coupled BEM-DES model
,”
Ocean Eng.
181
,
71
88
(
2019
).
12.
Howland
,
M. F.
,
Lele
,
S. K.
, and
Dabiri
,
J. O.
, “
Wind farm power optimization through wake steering
,”
Proc. Natl. Acad. Sci. U. S. A.
116
(
29
),
14495
14500
(
2019
).
13.
Jonkman
,
J.
,
Butterfield
,
S.
,
Musial
,
W.
, and
Scott
,
G.
, “
Definition of a 5-MW reference wind turbine for offshore system development
,”
Report No. NREL/TP-500-38060
(
National Renewable Energy Laboratory
,
2009
).
14.
Jonkman
,
J.
, “
Definition of the Floating System for Phase IV of OC3
,”
Report No. NREL/TP-500-47535
(
National Renewable Energy Laboratory
,
2010
).
15.
Jonkman
,
J.
and
Musial
,
W.
, “
Offshore code comparison collaboration (OC3) for IEA wind task 23 offshore wind technology and deployment
,”
Report No. NREL/TP-5000-48191
(
National Renewable Energy Laboratory
,
2010
).
16.
Kim
,
S. H.
,
Shin
,
H. K.
,
Joo
,
Y. C.
, and
Kim
,
K. H.
, “
A study of the wake effects on the wind characteristics and fatigue loads for the turbines in a wind farm
,”
Renewable Energy
74
,
536
543
(
2015
).
17.
Krogstad
,
P.-Å.
,
Saetran
,
L.
, and
Adaramola
,
M. S.
, “‘
Blind test 3’ calculations of the performance and wake development behind two in-line and offset model wind turbines
,”
J. Fluids Struct.
52
,
65
80
(
2015
).
18.
Kuo
,
J. Y.
,
Romero
,
D. A.
, and
Amon
,
C. H.
, “
A mechanistic semi-empirical wake interaction model for wind farm layout optimization
,”
Energy
93
,
2157
2165
(
2015
).
19.
Lei
,
H.
,
Zhou
,
D.
, and
Lu
,
J.
, “
The impact of pitch motion of a platform on the aerodynamic performance of a floating vertical axis wind turbine
,”
Energy
119
,
369
383
(
2017
).
20.
Lei
,
H.
,
Su
,
J.
,
Bao
,
Y.
,
Chen
,
Y.
,
Han
,
Z.
, and
Zhou
,
D.
, “
Investigation of wake characteristics for the offshore floating vertical axis wind turbines in pitch and surge motions of platforms
,”
Energy
166
,
471
489
(
2019
).
21.
Li
,
P.
,
Cheng
,
P.
,
Wan
,
D.
, and
Xiao
,
Q.
, “
Numerical simulations of wake flows of floating offshore wind turbines by unsteady actuator line model
,” in
the 9th International Workshop on Ship and Marine Hydrodynamics
,
Glasgow, United Kingdom
(Springer,
2015
), pp.
26
28
; available at https://dcwan.sjtu.edu.cn/userfiles/Numerical%20Simulations%20of%20Wake%20Flows%20of%20Floating%20Offshore%20Wind%20Turbines%20by%20Unsteady%20Actuator%20Line%20Model.pdf.
22.
Liu
,
Y.
,
Xiao
,
Q.
, and
Incecik
,
A.
, “
Investigation of the effects of platform motion on the aerodynamics of a floating offshore wind turbine
,”
J. Hydrodyn.
28
(
1
),
95
101
(
2016
).
23.
Liu
,
Y.
,
Xiao
,
Q.
, and
Incecik
,
A.
, “
Establishing a fully coupled CFD analysis tool for floating offshore wind turbines
,”
Renewable Energy
112
,
280
301
(
2017
).
24.
Lu
,
H.
and
Porté-Agel
,
F.
, “
Large-eddy simulation of a very large wind farm in a stable atmospheric boundary layer
,”
Phys. Fluids
23
(
6
),
065101
(
2011
).
25.
Menter
,
F. R.
, “
Two-equation eddy-viscosity turbulence models for engineering applications
,”
AIAA J.
32
(
8
),
1598
1605
(
1994
).
26.
Nagel
,
T.
,
Chauchat
,
J.
,
Wirth
,
A.
, and
Bonamy
,
C.
, “
On the multi-scale interactions between an offshore-wind-turbine wake and the ocean-sediment dynamics in an idealized framework—A numerical investigation
,”
Renewable Energy
115
,
783
796
(
2018
).
27.
Nanos
,
E. M.
,
Letizia
,
S.
,
Clemente
,
D. J. B.
,
Wang
,
C.
,
Rotea
,
M.
,
Iungo
,
V. I.
, and
Bottasso
,
C. L.
, “
Vertical wake deflection for offshore floating wind turbines by differential ballast control
,”
J. Phys.: Conf. Ser.
1618
,
022047
(
2020
).
28.
Obhrai
,
C.
,
Kalvig
,
S.
, and
Gudmestad
,
O. T.
, “
A review of current guidelines and research on wind modelling for the design of offshore wind turbines
,” in
ISOPE International Ocean and Polar Engineering Conference
(
ISOPE
,
2012
), p.
ISOPE-I
.
29.
Ortolani
,
A.
,
Persico
,
G.
,
Drofelnik
,
J.
,
Jackson
,
A.
, and
Campobasso
,
M. S.
, “
High-fidelity calculation of floating offshore wind turbines under pitching motion
,” in
Turbo Expo: Power for Land, Sea, and Air
(
American Society of Mechanical Engineers
,
2020
), Vol.
84249
, p.
V012T42A012
.
30.
Pierella
,
F.
,
Krogstad
,
P. A.
, and
Saetran
,
L.
, “
Blind test 2 calculations for two in-line model wind turbines where the downstream turbine operates at various rotational speeds
,”
Renewable Energy
70
,
62
77
(
2014
).
31.
Rezaeiha
,
A.
and
Micallef
,
D.
, “
Wake interactions of two tandem floating offshore wind turbines: CFD analysis using actuator disc model
,”
Renewable Energy
179
,
859
876
(
2021
).
32.
Rockel
,
S.
,
Peinke
,
J.
,
Hölling
,
M.
, and
Cal
,
R. B.
, “
Wake to wake interaction of floating wind turbine models in free pitch motion: An eddy viscosity and mixing length approach
,”
Renewable Energy
85
,
666
676
(
2016
).
33.
Rodrigues
,
S.
,
Restrepo
,
C.
, and
Kontos
,
E.
, “
Trends of offshore wind projects
,”
Renewable Sustainable Energy Rev.
49
,
1114
1135
(
2015
).
34.
Schwanitz
,
V. J.
and
Wierling
,
A.
, “
Offshore wind investments—Realism about cost developments is necessary
,”
Energy
106
,
170
181
(
2016
).
35.
Shaler
,
K.
,
Kecskemety
,
K. M.
, and
McNamara
,
J. J.
, “
Benchmarking of a free vortex wake model for prediction of wake interactions
,”
Renewable Energy
136
,
607
620
(
2019
).
36.
Shen
,
X.
,
Chen
,
J.
, and
Hu
,
P.
, “
Study of the unsteady aerodynamics of floating wind turbine
,”
Energy
145
,
793
809
(
2018
).
37.
Shen
,
Z. R.
,
Cao
,
H. J.
, and
Wan
,
D. C.
, “
Manual of CFD solver for ship and ocean engineering flows: Naoe-FOAM-SJTU
,” in
Technical Report for Solver Manual
(
Shanghai Jiao Tong University
,
2012
).
38.
Shin
,
D.
and
Ko
,
K.
, “
Experimental study on application of nacelle-mounted LiDAR for analyzing wind turbine wake effects by distance
,”
Energy
243
,
123088
(
2022
).
39.
Shives
,
M.
and
Crawford
,
C.
, “
Tuned actuator disk approach for predicting tidal turbine performance with wake interaction
,”
Int. J. Mar. Energy.
17
,
1
20
(
2017
).
40.
Sørensen
,
J. N.
and
Shen
,
W. Z.
, “
Numerical modeling of wind turbine wakes
,”
J. Fluids Eng.
124
(
2
),
393
399
(
2002
).
41.
Sturge
,
D.
,
Sobotta
,
D.
,
Howell
,
R.
,
While
,
A.
, and
Lou
,
J.
, “
A hybrid actuator disc—Full rotor CFD methodology for modelling the effects of wind turbine wake interactions on performance
,”
Renewable Energy
80
,
525
537
(
2015
).
42.
Sun
,
X.
,
Huang
,
D.
, and
Wu
,
G.
, “
The current state of offshore wind energy technology development
,”
Energy
41
(
1
),
298
312
(
2012
).
43.
Tran
,
T. T.
and
Kim
,
D. H.
, “
The aerodynamic interference effects of a floating offshore wind turbine experiencing platform pitching and yawing motions
,”
J. Mech. Sci. Technol.
29
(
2
),
549
561
(
2015
).
44.
Tran
,
T. T.
and
Kim
,
D. H.
, “
Fully coupled aero-hydrodynamic analysis of a semi-submersible FOWT using a dynamic fluid body interaction approach
,”
Renewable Energy
92
,
244
261
(
2016a
).
45.
Tran
,
T. T.
and
Kim
,
D. H.
, “
A CFD study into the influence of unsteady aerodynamic interference on wind turbine surge motion
,”
Renewable Energy
90
,
204
228
(
2016b
).
46.
Troldborg
,
N.
,
Sorensen
,
J. N.
, and
Mikkelsen
,
R.
, “
Numerical simulations of wake characteristics of a wind turbine in uniform inflow
,”
Wind Energy
13
(
1
),
86
99
(
2010
).
47.
Troldborg
,
N.
,
Larsen
,
G. C.
,
Madsen
,
H. A.
,
Hansen
,
K. S.
,
Srensen
,
J. N.
, and
Mikkelsen
,
R.
, “
Numerical simulations of wake interaction between two wind turbines at various inflow conditions
,”
Wind Energy
14
(
7
),
859
876
(
2011
).
48.
Wen
,
B.
,
Dong
,
X.
,
Tian
,
X.
,
Peng
,
Z.
, and
Zhang
,
W.
, “
Influences of surge motion on the power and thrust characteristics of an offshore floating wind turbine
,”
Energy
141
,
2054
2068
(
2018a
).
49.
Wen
,
B.
,
Dong
,
X.
,
Tian
,
X.
,
Peng
,
Z.
, and
Zhang
,
W.
, “
The power performance of an offshore floating wind turbine in platform pitching motion
,”
Energy
154
,
508
521
(
2018b
).
50.
Wen
,
B.
,
Tian
,
X.
,
Zhang
,
Q.
,
Dong
,
X.
,
Peng
,
Z.
,
Zhang
,
W.
, and
Wei
,
K.
, “
Wind shear effect induced by the platform pitch motion of a spar-type floating wind turbine
,”
Renewable Energy
135
,
1186
1199
(
2019
).
51.
Wu
,
Y. T.
and
Porté-Agel
,
F.
, “
Modeling turbine wakes and power losses within a wind farm using LES: An application to the Horns Rev offshore wind farm
,”
Renewable Energy
75
,
945
955
(
2015
).
52.
Yan
,
X.
,
Chang
,
W.
,
Cui
,
S.
,
Rasool
,
A.
,
Jia
,
J.
, and
Sun
,
Y.
, “
Recurrence of sub-synchronous oscillation accident of Hornsea wind farm in UK and its suppression strategy
,”
Energies
14
(
22
),
7685
(
2021
).
53.
Yang
,
K.
,
Kwak
,
G.
,
Cho
,
K.
, and
Huh
,
J.
, “
Wind farm layout optimization for wake effect uniformity
,”
Energy
183
,
983
995
(
2019
).
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