ECN publication
Modelling of rotational augmentation based on engineering considerations and measurements
Published by: Publication date:
ECN Wind Energy 1-11-2004
ECN report number: Document type:
ECN-RX--04-131 Conference Paper
Number of pages: Full text:
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Presented at: European Wind Energy Conference 2004, London, UK, 22-25 november 2004.


For wind turbines the effects of rotation lead to larger aerodynamic power and thrust compared to predictions based on 2D aerodynamic coefficients, which has been the subject of investigation for decades. Most models that account for the effects of rotation are in terms of increased lift or delay of stall to larger angles of attack. A model is presented on basis of a description of the separated flow at the trailing-edge. It includes the effect of the local speed ratio and it also gives a correction for the drag. This approach led to a so-called 'centrifugal pumping' correction model for the normal force coefficient together with a delay of separation to larger angles of attack. The centrifugal pumping model gave a good fit to both the measured lift anddrag coefficients from the NASA-Ames wind tunnel, but does not yet describe the reduction of the coefficients at the tip and the strong increase of coefficients near the root.

A comparison is presented with predicted rotating aerodynamic coefficients for the UAE Phase-IV rotor of NREL, which was measured in the NASA-Ames wind tunnel in the spring of 2000. These comparisons also included the Navier-stokes calculations with EllipSys3D by Johansen (Riso). Although the 'end effects' were not yet included, the model presented here also deals with the drag coefficient.

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