The accurate prediction of airfoil polars over the whole range of angles of attack and for different Reynolds numbers is pivotal to ensure an accurate prediction of wind turbine aerodynamic performance. In particular, modeling correctly the deep-stall and post-stall airfoil behavior is essential to reproduce reliable power and thrust curves for high wind conditions, especially as far as stall-controlled wind turbines are concerned. This need is even more urgent in vertical-axis wind turbines, in which the airfoils do experience a continuous variation of the angle of attack, exceeding the stall limit even in normal operating points. This paper presents a new method for extending an existing database of airfoil aerodynamic coefficients, e.g. in the common ranges of aeronautical references, over the ±180° range of angles of attack for an arbitrary airfoil shape. Moving from a few basic geometric data, as maximum thickness, camber and leading-edge radius, the whole curves of lift and drag coefficients are reconstructed starting from deep-stall conditions. The proposed correlation is compared to different models for the post-stall extrapolation of the airfoil behavior and experimental data, showing a good agreement with experimental polars for both symmetrical and cambered airfoils.

A generalized method to extend airfoil polars over the full range of angles of attack / Battisti, L.; Dell'Anna, S.; Raciti Castelli, M.; Brighenti, A.. - In: RENEWABLE ENERGY. - ISSN 0960-1481. - 155:(2020), pp. 862-875. [10.1016/j.renene.2020.03.150]

A generalized method to extend airfoil polars over the full range of angles of attack

Battisti L.;Dell'Anna S.;Raciti Castelli M.;Brighenti A.
2020

Abstract

The accurate prediction of airfoil polars over the whole range of angles of attack and for different Reynolds numbers is pivotal to ensure an accurate prediction of wind turbine aerodynamic performance. In particular, modeling correctly the deep-stall and post-stall airfoil behavior is essential to reproduce reliable power and thrust curves for high wind conditions, especially as far as stall-controlled wind turbines are concerned. This need is even more urgent in vertical-axis wind turbines, in which the airfoils do experience a continuous variation of the angle of attack, exceeding the stall limit even in normal operating points. This paper presents a new method for extending an existing database of airfoil aerodynamic coefficients, e.g. in the common ranges of aeronautical references, over the ±180° range of angles of attack for an arbitrary airfoil shape. Moving from a few basic geometric data, as maximum thickness, camber and leading-edge radius, the whole curves of lift and drag coefficients are reconstructed starting from deep-stall conditions. The proposed correlation is compared to different models for the post-stall extrapolation of the airfoil behavior and experimental data, showing a good agreement with experimental polars for both symmetrical and cambered airfoils.
Battisti, L.; Dell'Anna, S.; Raciti Castelli, M.; Brighenti, A.
A generalized method to extend airfoil polars over the full range of angles of attack / Battisti, L.; Dell'Anna, S.; Raciti Castelli, M.; Brighenti, A.. - In: RENEWABLE ENERGY. - ISSN 0960-1481. - 155:(2020), pp. 862-875. [10.1016/j.renene.2020.03.150]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11572/331894
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