The Comparison of Form Drag and Profile Dragof a Wind Turbine Blade Section in Pitching Oscillation

Extensive wind tunnel tests have been conducted to investigate the unsteady flow field over and behind a 2D model of a 660 kW wind turbine blade section in pitching motion. The surface pressure and wake dynamic pressure variation at a distance of 1.5 chord length from trailing edge were measured by pressure transducers during several oscillating cycles at 3 reduced frequencies and oscillating amplitudes. Moreover, form drag and linear momentum deficit are extracted and compared at various conditions. The results show that the wake velocity field and surface pressure of the model have similar behavior before and after the airfoil beyond the static stall angle of attack. In addition, the effects of reduced frequency and oscillation amplitudes are discussed.

Authors:

• M. R. Soltani
• M. Seddighi
• M. Mahmoudi

Keywords:

• Pitching motion
• form drag
• Profile drag
• windturbine.

References:

[1] McCroskey, W. J., "Unsteady Airfoils", Annual Rev. Fluid Mech. U.S.
Army Aerodynamics Laboratory and NASA, pp. 285-309, 1982.
[2] Fan, Y., "Identification of an Unsteady Aerodynamic Model up to High
Angle of Attack Regime," P.H.D Thesis, Virginia Polytechnic Institute
and State University, 1997.
[3] Maresca, C., Favier, D., and Rebont, J., "Experiments on an airfoil at
high angle of incidence in longitudinal oscillations", Journal of Fluid
mechanics, vol.92, 1979, pp. 671-690.
[4] Broeren, A. P., and Bragg, M. B., "Spanwise variation in the unsteady
stalling flowfields of two-dimensional airfoil models"., AIAA Journal ,
vol. 39 , no. 9 , Sept. , 2001, pp. 1641-1651.
[5] Walker, J. M., Helin H. E., and Chow, D. C. , B. E , " Unsteady surfaces
pressure measurement on a pitching airfoil" , AIAA-85-0532, AIAA
Shear Flow Control Conference , March 12-14 , 1985.
[6] Peter Fuglsang, Ioannis Antoniou, Niels N. S├©rensen, Helge Aa.
Madsen, "Validation of a Wind Tunnel Testing Facility for Blade
Surface Pressure Measurements," Ris├©-R-981(EN), 1998
[7] Carr, L. W., "Progress in Analysis and Prediction of Dynamic Stall,"
Journal of Aircraft, Vol. 25, Jan 1988, pp. 6-17.
[8] McAlister, K. W., and Caw, L. W., "Water Tunnel Visualization of
Dynamic Stall," Non steady Fluid Dynamics (ed. by Crow, P.E., and
Miller, J. A.), p. 103, 1978.
[9] Satyanarayana, B., "Unsteady Wake Measurements of Airfoils and
Cascades," AIAA Journal, Vol. 15, May 1977, pp. 613-618.
[10] Jones, K.D., Dohring, C.M., and Platzer, M.F. "Wake Structures Behind
Plunging Airfoils: A Comparison Of Numerical And Experimental
Results," 34th Aerospace Sciences Meeting & Exhibit, AIAA 96−0078,
1996.
[11] Ho, C,-M. and Chen, S.-H. "Unsteady Wake of a Plunging Airfoil,"
AIAA Journal, Vol.19, Nov. 1981, pp. 1492-1494.
[12] Park, S.O., Kim, J.S, Lee, B.I., "Hot-Wire Measurements of Near Wakes
Behind an Oscillating Airfoil," AIAA Journal Vol. 28, No. 1, 1989.
[13] Koochesfahani, M. M, "Vortical Patterns in the Wake of an Oscillating
Airfoil," AIAA Journal, Vol. 27, No. 9, Sep. 1989, pp. 1200-1205.
[14] Panda, J., and Zaman, K.B.M.Q "Experimental Investigation of the Flow
Field of an Ocillating Airfol and Estimation of Lift from Wake
Survays," Journal of Fluid Mechanics, Vol. 265, 1994, pp. 65-95.
[15] Leishman, J. G., "Challenges in modeling the unsteady aerodynamics of
wind turbines", AIAA 2002-0037, 21st ASME Wind Energy
Symposium and the 40th AIAA Aerospace Sciences Meeting , Jan. 14-
17, 2002.
[16] Younsi, R., El-Batanong , I. Tritsch , J., Naji, H., and Landjerit, B.,
"Dynamic study of a wind turbine blade with horizontal axis" ,Sur. J.
Mech. A/Solids 20, 2001, pp. 241-252.
[17] Huyer, S. A., Simms, D. A., and Robinson, M. C. , "Unsteady
aerodynamics associated with a horizontal-axis wind turbine" , AIAA
Journal , vol. 34, No. 7 , 1996 ,pp. 1410-1419.
[18] Hansen, A. C, Butterfield, C. P, "Aerodynamics of Horizontal -Axis
Wind Turbines", Annul Rev. Fluid Mech. 1993.25:115, 1993.
[19] Gustave Paul Corten, "Flow Separation on Wind Turbine Blades"
[20] Tangler, Kocurek, J. D., "Wind Turbine Post-Stall Airfoil Performance
Characteristics Guidelines for Blade-Element Momentum Methods",
43rd AIAA Aerospace Sciences Meeting and Exhibit, AIAA, 2005.
[21] Kirk Gee Pierce, "Wind Turbine Load Prediction Using The Beddoes-
Leishman Model For Unsteady Aerodynamics And Dynamic Stall",
Master of Science Thesis, The University of Utah, 1996
[22] Soltani, M. R., Rasi, F., Seddighi, M., and Bakhshalipour, A."An
Experimental Investigation of Time lage in Pressure Measuring System"
, Ankara International Aerospace Conference, Turkey, 2005.
[23] Rae, W. H., and Pope, A. , Low Speed Wind Tunnel Testing, Second
edition, John Wiley and Sons, 2000.
[24] Satyanarayana B. and C. S. Lee "Unsteady Wake Measurements of an
Oscillating Flap at Transonic Speeds," AIAA Journal, Vol. 24, No. 12,
1986.