This study shows the results of pressure distribution measurements on a rotor blade of a horizontal axis wind turbine under various yawed operations. The experiments are carried out in a wind tunnel with a $2.4m$ diameter test rotor. In the measurements, the power curve and pressure distributions are measured for different azimuth angles. By increasing yaw angle, the maximum value of power coefficient of the rotor decreases. The sign of the yaw angle does not have any effect on power performance. The aerodynamic forces are discussed using the axial and rotational force coefficients for each azimuth angle. In the case of higher tip speed ratios, the blade section passing on the upstream side in yawed operations has a greater contribution to the rotor torque than that on the downstream side. In this tip speed range, the aerodynamic forces at the 70% radius section appear proportional to the angle of attack. In the case of the lower tip speed ratios, the blade on the downstream side does not contribute to rotor torque, which appears to result from separation.

1.
Snel
,
H.
, 1998, “
Review of the Present Status of Rotor Aerodynamics
,”
Wind Energy
1095-4244,
1
(
S1
), pp.
46
69
.
2.
Vermeer
,
L. J.
,
Sørensen
,
J. N.
, and
Crespo
,
A.
, 2003, “
Wind Turbine Wake Aerodynamics
,”
Prog. Aerosp. Sci.
0376-0421,
39
(
6–7
), pp.
467
510
.
3.
Schepers
,
J. G.
,
Brand
,
A. J.
,
Bruining
,
A.
,
Graham
,
J. M. R.
,
Hand
,
M. M.
,
Infield
,
D. G.
,
,
H. A.
,
Maeda
,
T.
,
Paynter
,
J. H.
,
van Rooij
,
R.
,
Shimizu
,
Y.
,
Simms
,
D. A.
, and
Stefanatos
,
N.
, 2002, “
Final Report of IEA Annex XVIII: ‘Enhanced Field Rotor Aerodynamics Database
,’” ECN-C-02-016, p.
353
.
4.
Maeda
,
T.
,
Ismaili
,
E.
,
Kawabuchi
,
H.
, and
,
Y.
, 2005, “
Surface Pressure Distribution on a Blade of a 10m Diameter HAWT (Field Measurements Versus Wind Tunnel Measurements)
,”
ASME J. Sol. Energy Eng.
0199-6231,
127
(
2
), pp.
185
191
.
5.
Simms
,
D.
,
Schreck
,
S.
,
Hand
,
M.
, and
Fingersh
,
L. J.
, 2001, “
NREL Unsteady Aerodynamics Experiment in the NASA-Ames Wind Tunnel: A Comparison of Predictions to Measurements
,” NREL∕TP-500-29494.
6.
Imamura
,
H.
,
Takezaki
,
D.
,
Hasegawa
,
Y.
,
Kikuyama
,
K.
, and
Kobayashi
,
K.
, 2004, “
Numerical Analysis of a Local Angle of Attack to HAWT Rotor Blade in Unsteady Flow Conditions
,”
Proceedings of European Wind Energy Conference & Exhibition 2004
,
London, UK
, CD-ROM, p.
8
.
7.
Pesmajoglou
,
S.
, and
Graham
,
J. M. R.
, 1993, “
Prediction of Yaw Loads on a Horizontal Axis Wind Turbine
,”
Proceedings of European Community Wind Energy Conference
,
Lübeck-Travemünde
,
Germany
, pp.
420
423
.
8.
Haans
,
W.
,
Sant
,
T.
,
van Kuik
,
G.
, and
van Bussel
,
G.
, 2005, “
Measurement of Tip Vortex Paths in the Wake of a HAWT Under Yawed Flow Conditions
,”
ASME J. Sol. Energy Eng.
0199-6231,
127
(
4
), pp.
456
463
.
9.
Medici
,
D.
, and
Alfredsson
,
P. H.
, 2006, “
Measurements on a Wind Turbine Wake: 3D Effects and Bluff Body Vortex Shedding
,”
Wind Energy
1095-4244,
9
(
3
), pp.
219
236
.
10.
Grant
,
I.
,
Parkin
,
P.
, and
Wang
,
X.
, 1997, “
Optical Vortex Tracking Studies of a Horizontal Axis Wind Turbine in Yaw Using Laser-Sheet, Flow Visualization
,”
Exp. Fluids
0723-4864,
23
, pp.
513
519
.
11.
Maeda
,
T.
,
,
Y.
,
Sakai
,
Y.
, and
Takahara
,
N.
, 2005, “
Experimental Study on Flow Around Blades of Horizontal Axis Wind Turbine in Wind Tunnel
,”
Trans. Jpn. Soc. Mech. Eng., Ser. B
0387-5016,
71
(
701
), pp.
171
176
.
12.
Maeda
,
T.
,
,
Y.
,
Sakai
,
Y.
, and
Takahara
,
N.
, 2005, “
Experimental Study on Flow Around Blades of Horizontal Axis Wind Turbine in Wind Tunnel (Second Report Studies on the Flow Around Blade Based on Pressure Distribution)
,”
Trans. Jpn. Soc. Mech. Eng., Ser. B
0387-5016,
71
(
705
), pp.
1383
1389
.
13.
Amandolèse
,
X.
, and
Szèchényi
,
E.
, 2004, “
Experimental Study of the Effect of Turbulence on a Section Model Blade Oscillating in Stall
,”
Wind Energy
1095-4244,
7
(
4
), pp.
267
282
.