A better comprehension of the aerodynamic behavior of rotating airfoils in Darrieus vertical-axis wind turbines (VAWTs) is crucial both for the further development of these machines and for improvement of conventional design tools based on zero- or one-dimensional models (e.g., blade element momentum (BEM) models). When smaller rotors are designed with high chord-to-radius (c/R) ratios so as not to limit the blade Reynolds number, the performance of turbine blades has been suggested to be heavily impacted by a virtual camber effect imparted on the blades by the curvilinear flow they experience. To assess the impact of this virtual camber effect on blade and turbine performance, a standard NACA 0018 airfoil and a NACA 0018 conformally transformed such that the airfoil's chord line follows the arc of a circle, where the ratio of the airfoil's chord to the circle's radius is 0.25 were considered. For both airfoils, wind tunnel tests were carried out to assess their aerodynamic lift and drag coefficients for Reynolds numbers of interest for Darrieus VAWTs. Unsteady computational fluid dynamics (CFD) calculations have been then carried out to obtain curvilinear flow performance data for the same airfoils mounted on a Darrieus rotor with a c/R of 0.25. The blade incidence and lift and drag forces were extracted from the CFD output using a novel incidence angle deduction technique. According to virtual camber theory, the transformed airfoil in this curvilinear flow should be equivalent to the NACA 0018 in rectilinear flow, while the NACA0018 should be equivalent to the inverted transformed airfoil in rectilinear flow. Comparisons were made between these airfoil pairings using the CFD output and the rectilinear performance data obtained from the wind tunnel tests and xfoil output in the form of pressure distributions and lift and drag polars. Blade torque coefficients and turbine power coefficient are also presented for the CFD VAWT using both blade profiles.

References

References
1.
Paraschivoiu
,
I.
,
2002
,
Wind Turbine Design With Emphasis on Darrieus Concept
,
Polytechnic International Press
,
Montreal, QC
.
2.
Kirke
,
B. K.
,
1998
, “
Evaluation of Self-Starting Vertical Axis Wind Turbines for Standalone Applications
,” Ph.D. thesis, Griffith University, Gold Coast, Australia.
3.
Balduzzi
,
F.
,
Bianchini
,
A.
,
Maleci
,
R.
,
Ferrara
,
G.
, and
Ferrari
,
L.
,
2015
, “
Blade Design Criteria to Compensate the Flow Curvature Effects in H-Darrieus Wind Turbines
,”
ASME J. Turbomach.
,
137
(
1
), p.
011006
.
4.
Marten
,
D.
,
Wendler
,
J.
,
Pechlivanoglou
,
G.
,
Nayeri
,
C. N.
, and
Paschereit
,
C. O.
,
2013
, “
Qblade: An Open Source Tool for Design and Simulation of Horizontal and Vertical Axis Wind Turbines
,”
Int. J. Emerging Technol. Adv. Eng.
,
3
(
special issue 3
), pp.
264
269
.
5.
Bianchini
,
A.
,
Ferrari
,
L.
, and
Magnani
,
S.
,
2011
, “
Start-Up Behavior of a Three-Bladed H-Darrieus VAWT: Experimental and Numerical Analysis
,”
ASME
Paper No. GT2011-45882.
6.
Bianchini
,
A.
,
Balduzzi
,
F.
,
Rainbird
,
J.
,
Peiro
,
J.
,
Graham
,
J. M. R.
,
Ferrara
,
G.
, and
Ferrari
,
L.
,
2015
, “
An Experimental and Numerical Assessment of Airfoil Polars for Use in Darrieus Wind Turbines—Part II: Post-Stall Data Extrapolation Methods
,”
ASME J. Eng. Gas Turbine Power
(in press).
7.
Du
,
L.
,
Berson
,
A.
, and
Dominy
,
R. G.
,
2015
, “
NACA0018 Behaviour at High Angles of Attack and at Reynolds Numbers Appropriate for Small Wind Turbines
,”
Proc. Inst. Mech. Eng., Part C
,
229
(
11
), pp.
2007
2022
.
8.
Sheldahl
,
R. E.
, and
Klimas
,
P. C.
,
1981
, “
Aerodynamic Characteristics of Seven Symmetrical Airfoil Sections Through 180-Degree Angle of Attack for Use in Aerodynamic Analysis of Vertical Axis Wind Turbines
,” Sandia National Laboratories, Albuquerque, NM, Technical Report No. SAND80-2114.
9.
Timmer
,
W. A.
,
2008
, “
Two-Dimensional Low-Reynolds Number Wind Tunnel Results for Airfoil NACA0018
,”
Wind Eng.
,
32
(
6
), pp.
525
537
.
10.
Migliore
,
P. G.
,
Wolfe
,
W. P.
, and
Fanucci
,
J. B.
,
1980
, “
Flow Curvature Effects on Darrieus Turbine Blade Aerodynamics
,”
J. Energy
,
4
(
2
), pp.
49
55
.
11.
Bianchini
,
A.
,
Ferrari
,
L.
, and
Carnevale
,
E. A.
,
2011
, “
A Model to Account for the Virtual Camber Effect in the Performance Prediction of an H-Darrieus VAWT Using the Momentum Models
,”
Wind Eng.
,
35
(
4
), pp.
465
482
.
12.
Islam
,
M.
,
Ting
,
D.
, and
Fartaj
,
A.
,
2007
, “
Desirable Airfoil Features for Smaller-Capacity Straight-Bladed VAWT
,”
Wind Eng.
,
31
(
3
), pp.
165
196
.
13.
Selig
,
M. S.
,
Deters
,
R. W.
, and
Williamson
,
G. A.
,
2011
, “
Wind Tunnel Testing Airfoils at Low Reynolds Numbers
,”
AIAA
Paper No. 2011-875.
14.
Engineering Sciences Data Unit
,
1978
, “
Lift-Interference and Blockage Corrections for Two-Dimensional Subsonic Flow in Ventilated and Closed Wind-Tunnels
,” IHS ESDU, Denver, CO, Technical Report No. ESDU 76028.
15.
Drela
,
M.
, and
Youngren
,
H.
, 2001, “XFoil User Guide,” accessed Oct. 2,
2014
, http://web.mit.edu/drela/Public/web/xfoil
16.
“xflr5,” accessed Oct. 13,
2014
, www.xflr5.com/xflr5.htm
17.
Du
,
L.
,
Berson
,
A.
, and
Dominy
,
R. G.
,
2014
, “
NACA0018 Behaviour at High Angles of Attack and at Reynolds Numbers Appropriate for Small Wind Turbines
,” School of Engineering and Computing Sciences, Durham University, Durham, UK, ECS Technical Report No. 2014/08.
18.
Ansys
,
2013
, “
Fluent Theory Guide
,” Release 14.5.4,
Ansys
, Inc., Canonsburg, PA, www.ansys.com
19.
Balduzzi
,
F.
,
Bianchini
,
A.
,
Maleci
,
R.
,
Ferrara
,
G.
, and
Ferrari
,
L.
,
2016
, “
Critical Issues in the CFD Simulation of Darrieus Wind Turbines
,”
Renewable Energy
,
85
, pp.
406
418
.
20.
Maître
,
T.
,
Amet
,
E.
, and
Pellone
,
C.
,
2013
, “
Modeling of the Flow in a Darrieus Water Turbine: Wall Grid Refinement Analysis and Comparison With Experiments
,”
Renewable Energy
,
51
, pp.
497
512
.
21.
Howell
,
R.
,
Qin
,
N.
,
Edwards
,
J.
, and
Durrani
,
N.
,
2010
, “
Wind Tunnel and Numerical Study of a Small Vertical Axis Wind Turbine
,”
Renewable Energy
,
35
(
2
), pp.
412
422
.
22.
Beri
,
H.
, and
Yao
,
Y.
,
2011
, “
Effect of Camber Airfoil on Self Starting of Vertical Axis Wind Turbine
,”
J. Environ. Sci. Technol.
,
4
(
3
), pp.
302
312
.
23.
Raciti Castelli
,
M.
,
Englaro
,
A.
, and
Benini
,
E.
,
2011
, “
The Darrieus Wind Turbine: Proposal for a New Performance Prediction Model Based on CFD
,”
Energy
,
36
(
8
), pp.
4919
4934
.
24.
Rossetti
,
A.
, and
Pavesi
,
G.
,
2013
, “
Comparison of Different Numerical Approaches to the Study of the H-Darrieus Turbines Start-Up
,”
Renewable Energy
,
50
, pp.
7
19
.
25.
Balduzzi
,
F.
,
Bianchini
,
A.
,
Gigante
,
F. A.
,
Ferrara
,
G.
,
Campobasso
,
M. S.
, and
Ferrari
,
L.
,
2015
, “
Parametric and Comparative Assessment of Navier–Stokes CFD Methodologies for Darrieus Wind Turbine Performance Analysis
,”
ASME
Paper No. GT2015-42663.
26.
Menter
,
F. R.
,
1994
, “
Two-Equation Eddy-Viscosity Turbulence Models for Engineering Applications
,”
AIAA J.
,
32
(
8
), pp.
1598
1605
.
27.
Menter
,
F. R.
,
Langtry
,
R. B.
,
Likki
,
S. R.
,
Suzen
,
Y. B.
,
Huang
,
P. G.
, and
Völker
,
S.
,
2004
, “
A Correlation-Based Transition Model Using Local Variables. Part 1—Model Formulation
,”
ASME
Paper No. GT2004-53452.
28.
Langtry
,
R. B.
, and
Menter
,
F. R.
,
2009
, “
Correlation-Based Transition Modeling for Unstructured Parallelized Computational Fluid Dynamics Codes
,”
AIAA J.
,
47
(
12
), pp.
2894
2906
.
29.
Lanzafame
,
R.
,
Mauro
,
S.
, and
Messina
,
M.
,
2014
, “
2D CFD Modeling of H-Darrieus Wind Turbines Using a Transition Turbulence Model
,”
Energy Procedia
,
45
, pp.
131
140
.
30.
Guntur
,
S.
, and
Sørensen
,
N. N.
,
2012
, “
Evaluation of Several Methods of Determining the Angle of Attack on Wind Turbine Blades, The Science of Making Torque From Wind 2012, Oldenburg, Germany
,”
DTU Wind Energy
,
Technical University of Denmark
, Lyngby, Denmark.
31.
Hansen
,
M. O. L.
,
Sørensen
,
N. N.
,
Sørensen
,
J. N.
, and
Michelsen
,
J. A.
,
1997
, “
Extraction of Lift, Drag and Angle of Attack From Computed 3-D Viscous Flow Around a Rotating Blade
,” European Wind Energy Conference (
EWEC 1997
), Dublin, Ireland, Oct. 6–9, pp.
499
501
.
You do not currently have access to this content.