ECN publication
Quasi-steady aerodynamic coefficients at a large range of angles of attack
Published by: Publication date:
ECN 1996
ECN report number: Document type:
ECN-C--95-059 ECN publication
Number of pages: Full text:
62 Download PDF  

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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