Riso̸ has developed a dynamic stall model that is used to analyze and reproduce open air blade section measurements as well as wind tunnel measurements. The dynamic stall model takes variations in both angle of attack and flow velocity into account. The paper gives a brief description of the dynamic stall model and presents results from analyses of dynamic stall measurements for a variety of experiments with different airfoils in wind tunnel and on operating rotors. The wind tunnel experiments comprises pitching as well as plunging motion of the airfoils. The dynamic stall model is applied for derivation of aerodynamic damping characteristics for cyclic motion of the airfoils in flapwise and edgewise direction combined with pitching. The investigation reveals that the airfoil dynamic stall characteristics depend on the airfoil shape, and the type of motion (pitch, plunge). The aerodynamic damping characteristics, and thus the sensitivity to stall induced vibrations, depend highly on the relative motion of the airfoil in flapwise and edgewise direction, and on a possibly coupled pitch variation, which is determined by the structural characteristics of the blade.

1.
Rasmussen, F., 1994, “Dynamic Stall of a Wind Turbine Blade Section,” Proceedings of lEA-meeting on Aerodynamics, Technical University of Denmark, Lyngby, Denmark.
2.
Carta, F. O., et al., 1972, “Investigation of Airfoil Dynamic Stall and its Influence on Helicopter Control Loads,” USAAMRDL Technical Report 72-51, September 1972,
3.
Madsen, H. A., 1990, “Measured Airfoil Characteristics of Three Blade Segments on a 19-m HAWT Rotor,” Proceedings of Ninth ASME Wind Energy Symposium, Presented at the Thirteenth Annual Energy-Sources Technology Conference and Exhibition, New Orleans, Louisiana, January 14–18, 1990.
4.
Bjo¨rck, A., 1995, “Dynamic Stall and Three-dimensional Effects,” FFA TN 1995-31, The Aeronautical Research Institute of Sweden, Bromma, Sweden.
5.
Hoffman, M. J., Ramsay, R. R., and Gregorek, G. M., 1994, “Unsteady Aerodynamic Performance of Wind Turbine Airfoils,” Proceedings of AWEA Wind-Power ’94, Minneapolis, Minnesota.
6.
Petersen, J. T., “The Aeroelastic Code HawC—Model and Comparisons,” In proceedings of State of the Art of Aeroelastic Codes for Wind Turbine Calculations, 28th Meeting of Experts, International Energy Agency, Annex XI. Editor B. Maribo Pedersen, Technical University of Denmark, Lyngby, April 11-12 1996, pp. 129–135.
7.
Petersen, J. T., et al., 1998, Prediction of Dynamic Loads and Induced Vibrations in Stall, Riso̸-R–1045(EN). Riso̸ National Laboratory.
8.
Leishman, J. G., and Beddoes, T. S., “A Generalised Model for Unsteady Airfoil Behaviour and Dynamic Stall Using the Indical Method,” Presented at the 42nd Annual Forum of the American Helicopter Society, Washington D.C. June 1986.
9.
Tran, C. T., and Petot, D., “Semi-empirical model for the dynamic stall of airfoils in view of the application of a helicopter blade in forward flight,” 6th European Rotorcraft and Powered-Lift Aircraft Forum, Bristol, UK, September 1980.
10.
Schepers, J. G., et al., “Final Report of IEA Annex XIV: Field Rotor Aerodynamics,” Delft University of Technology, ECN-C—97-027. June 1997.
11.
Madsen, H. A. and Rasmussen, F., 1993, “Steady and Unsteady Wind Tunnel Measurements on a Blade Section,” Proceedings of IEA Meeting on the Aerodynamics of Wind Turbines, November 29-30, 1993, edited by J. M. Ward.
This content is only available via PDF.
You do not currently have access to this content.