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Title:
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Modelling of rotational augmentation based on engineering considerations and measurements
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Author(s):
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Published by:
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Publication date:
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ECN
Wind Energy
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1-11-2004
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ECN report number:
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Document type:
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ECN-RX--04-131
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Conference Paper
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Number of pages:
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Full text:
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12
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Download PDF
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Presented at: European Wind Energy Conference 2004, London, UK, 22-25 november 2004.
Abstract:
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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