Dynamic Stall on Rotating Airfoils: A Look at the N-Sequence Data from the NREL Phase VI Experiment

Abstract:

This paper presents an investigation on the combined effect of dynamic stall and rotational augmentation on wind turbine blades. Dynamic stall and rotational augmentation have previously been studied independently. The NREL Phase VI experiment was one large scale experiment that recorded 3D measurements on rotating and pitching airfoils, and using some these data the behaviour of the unsteady CL-α polars under the influence of rotation is investigated. Unsteady DES CFD computations of the Phase VI rotor in axial operation and continuous pitching conditions (reproducing conditions similar to the N-sequence experiments) for select cases have also been carried out using the in-house flow solver EllipSys3D. The resulting set of CL-α curves for the airfoils in rotation operating at various values of the frequency, the mean, and the amplitude of the angle of attack resulting from the CFD computations as well as those from the experiments are presented and discussed. Qualitative differences between dynamic stall occurrence on rotating and stationary airfoils are highlighted, procedures employed to extract the mean angle of attack from the available experimental data are discussed, and comments are made on the application of dynamic stall models in conjunction with 3D augmentation models on the rotating wind turbine blades.

• Periodical: Key Engineering Materials (Volumes 569-570)
• Pages: 611-619
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.569-570.611
• Online since: July 2013
• Authors: Srinivas Guntur, Niels N. Sørensen, Scott Schreck
• Keywords: Computational Fluid Dynamics (CFD), Dynamic Stall, NREL Phase VI, Rotational Augmentation, Unsteady DES

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