In the present paper it is first demonstrated that state of the art 3D CFD codes are capable of predicting the correct dependency of the integrated drag of a flat plate placed perpendicular to the flow. This is in strong contrast to previous 2D investigations of infinite plates, where computations are known to severely overpredict drag. We then demonstrate that the computed drag distribution along the plate span deviate from the general expectation of 2D behavior at the central part of the plate, an important finding in connection with the theoretical estimation of drag behavior on wind turbine blades. The computations additionally indicate that a “tip effect” is present that produces increased drag near the end of the plate, which is opposite of the assumptions generally used in drag estimation for blades. Following this several wind turbine blades are analyzed, ranging from older blades of approximately 10 meter length (LM 8.2) over more recent blades (LM 19.1) around 20 meters to two modern blades suited for megawatt size turbines. Due to the geometrical difference between the four blades, the simple dependency on aspect ratio observed for the plates are not recovered in this analysis. The turbine blades behave qualitatively very similar to the flat plates and the spanwise drag distributions show similar “tip effects.” For the turbine blades this effect is even more pronounced, because the tapering of the blades makes the tip effect spread to a larger part of the blades. The findings are supported by visualizations of the wake patterns behind the blades.

Issue Section:
Technical Papers
Keywords:
wind turbines, drag, computational fluid dynamics, turbulence, Navier-Stokes equations
Topics:
Blades, Computational fluid dynamics, Drag (Fluid dynamics), Flat plates, Wind turbines, Computation, Flow (Dynamics), Plates (structures)
1.
Ostawari
,
C.
, and
Naik
,
D.
,
1984
, “
Post Stall Studies of Untwisted Varying Aspect Ratio Blades with an NACA 4415 Airfoil Section—Part I
,”
Wind Eng.
,
8
(
3
), pp.
176
–
194
.
2.
Ostawari
,
C.
, and
Naik
,
D.
,
1984
, “
Post Stall Studies of Untwisted Varying Aspect Ratio Blades with an NACA 44XX Series Airfoil Section—Part II
,”
Wind Eng.
,
9
(
3
), pp.
149
–
164
.
3.
Dahlberg, J.-A., and Ronsten, G., 1994, “A Wind Tunnel Investigation of Tower Blockage Effects and Parking Loads on a E 5.35 M Horizontal Axis Wind Turbine,” In 5th European Wind Energy Association Conference and Exhibition, Copenhagen, Denmark, volume II, pp. 414–417, 10–14 October.
4.
Simms, D., Hand, M. M., Fingersh, L. J., and Jager, D. W., 1999, “Unsteady Aerodynamics Experiment Phases II–IV: Test Configurations and Available Data Campaigns” NREL/TP-500-25950, Nat. Ren. Energy Lab., Golden, CO.
5.
Dekker, J. W. M., de Groot, C. M., and Spath, M., 1989, “Mechanical Measurements on VSH 20-WPX-THR Rotor Blades at the ‘25 HAWT’ Rotor Test Facility—Part 1,” Ecn-89-35, The Netherlands Energy Research Foundation (ECN).
6.
Paulsen, U. S., 1989, “Aerodynamics of Full Scale, Non-rotating Wind Turbine Blade Under Natural Wind Conditions,” Risø-M-2768, Risø National Laboratory, Roskilde, Denmark.
7.
Brand, A. J., and Montgomerie, B., 1995, “Quasi-Steady Aerodynamic Coefficients at a Large Range of Angles of Attack,” Ecn-c-95-059, The Netherlands Energy Research Foundation (ECN).
8.
Montgomerie, B., 1996. Drag Coefficient Distribution on a Wing at 90 Degrees to the Wind. Ecn-c-95-061, The Netherlands Energy Research Foundation (ECN).
9.
Lindenburg, C., 2000, “Stall Coefficients, Aerodynamic Airfoil Coefficients at Large Angles of Attack,” In IEA Joint Action. Aerodynamics of Wind Turbines. 14th Symposium, pp. 133–148, Boulder, USA.
10.
Yang
,
S. L.
,
Chang
,
Y. L.
, and
Arici
,
O.
,
1995
, “
Navier-Stokes Computations of the NREL Airfoil Using a k−ω Turbulent Model at High Angles of Attack
,”
J. Sol. Energy Eng.
,
117
, pp.
304
–
310
.
11.
Bertagnolio, F., Sørensen, N. N., Johansen, J., and Fuglsang, P., 2001, “Wind Turbine Airfoil Catalogue,” Risø-R-1280-(EN), Risø National Laboratory, Roskilde, Denmark.
12.
Johansen, J., Sørensen, N. N., Michelsen, J. A., and Schreck, S., 2001, “Detached-Eddy Simulation of Flow Around the S809 Airfoil,” in European Wind Energy Conference & Exhibition, Copenhagen, Denmark, pp. 414–417, 2–6.
13.
Michelsen, J. A., 1992, “Basis3D—A Platform for Development of Multiblock PDE Solvers,” Technical Report AFM 92-05, Technical University of Denmark.
14.
Michelsen, J. A., 1994, “Block structured Multigrid Solution of 2D and 3D Elliptic PDE’s,” Technical Report AFM 94-06, Technical Univ.
15.
Sørensen, N. N., 1995, “General Purpose Flow Solver Applied to Flow over Hills,” Risø-R-827-(EN), Risø National Laboratory, Roskilde, Denmark.
16.
Rhie, C. M., 1981, “A Numerical Study of the Flow Past an Isolated Airfoil With Separation,” PhD thesis, Univ. of Illinois, Urbana-Champaign.
17.
Issa
,
R. I.
,
1985
, “
Solution of the Implicitly Discretized Fluid Flow Equations by Operator-Splitting
,”
J. Comput. Phys.
,
62
, pp.
40
–
65
.
18.
Issa
,
R. I.
,
Gosman
,
A. D.
, and
Watkins
,
A. P.
,
1986
, “
The Computation of Compressible and Incompressible Recirculating Flows by a Non-iterative Implicit Scheme
,”
J. Comput. Phys.
,
62
, pp.
66
–
82
.
19.
Khosla
,
P. K.
, and
Rubin
,
S. G.
,
1974
, “
A Diagonally Dominant Second-order Accurate Implicit Scheme
,”
Comput. Fluids
,
2
, pp.
207
–
209
.
20.
Menter, F. R., 1993, “Zonal Two Equation k−ω Turbulence Models for Aerodynamic Flows,” AIAA-paper-932906.
21.
Wilcox, D. C., 1991, “A Half Century Historical Review of the K−ω Model,” AIAA-91-0615.
22.
Menter
,
F. R.
,
1992
, “
Performance of Popular Turbulence Models for Attached and Separated Adverse Pressure Gradient Flows
,”
AIAA J.
,
30
(
8
), pp.
2066
–
2072
.
23.
Sørensen, N. N., 1998, “HypGrid2D a 2-D Mesh Generator,” Risø-R-1035-(EN), Risø National Laboratory, Roskilde, Denmark.
24.
Hoerner, S. F., 1965. Fluid-Dynamic Drag, Practical Information on Aerodynamic Drag and Hydrodynamic Resistance published by the author.
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