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Title:
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Application of a modified Theodorsen model to the estimation of aerodynamic forces and aeroelastic stability
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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--04-120
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Conference Paper
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Number of pages:
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Full text:
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7
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Download PDF
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Presented at: European Wind Energy Conference 2004, London, UK, 22-25 november 2004.
Abstract:
Unsteady
effects in attached flow are of importance for the damping of edge wise
vibrations, also for pitch regulated
wind turbines.
In a number
of aeroelastic codes, these effects are treated with the classical Theodorsen
model. This is the case when the Leishman Beddoes [1] model is used,
in which the Theodorsen model is included. However, Theodorsen?s model
is based on 2D flow. Although 2D flow is also the basis for profile
aerodynamics on rotating blades in the BEM method, especially the shed
wake part of the flow is definitely different in the rotating blade
case. The difference between the 2D and the 3D rotating case was quantified
in [2] as far as induced velocity is concerned. However in that paper,
no link was made to unsteady aerodynamic forces. This part is fully developed in the present
paper. The expression for aerodynamic lift is cast in the form of so
called quasi-steady lift force as often used in BEM modelling, plus
and additional part that results from the present theory. Also, a unsteady
drag force is identified and quantified.
Application
of the theory to the aerodynamic damping of in-plane vibrations will
be shown at the conference.
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