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Title:
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Quasi-steady aerodynamic coefficients at a large range of angles of attack
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Author(s):
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Published by:
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Publication date:
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ECN
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1996
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ECN report number:
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Document type:
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ECN-C--95-059
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ECN publication
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Number of pages:
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Full text:
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62
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Download PDF
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Abstract:
Aerodynamic data measured at a non-rotating rotor blade in thefree-stream wind was analysed with '2D (un)steady' analysis techniques. Time
series of the normal force coefficient cn and the angle of attack alpha
(small, medium and large average incidence) were analysed by identification
cn(alpha) loops, conditionally averaging against dalpha/dt correlating
cn(t) to alpha(t), and determining the parameters of a simple unsteady
lift model. It appeared that applying these '2D unsteady' techniques to the
'3D unsteady' data did not give useful results. Data obtained at
-180"ol and cd. Comparing these cl's and cd's to reference values
revealed large differences (cl: about 25%; cd: up to 100%) between the
averaged '3D unsteady' and the '2D steady' data. Taken together the failure
of the techniques and the large difference suggest that field data must not
be used for the tuning of model parameters. 21 figs, 10 tabs, 15 refs.
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