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Vortex formation around an oscillating and translating airfoil at large incidences

Published online by Cambridge University Press:  26 April 2006

Kazuo Ohmi ,
Madeleine Coutanceau ,
Ta Phuoc Loc  and
Annie Dulieu
Kazuo Ohmi
Affiliation:
Osaka University, Faculty of Language and Culture, Osaka 560, Japan
Madeleine Coutanceau
Affiliation:
Laboratoire de Mécanique des Fluides, Université de Poitiers, 86022 Poitiers Cedex, France
Ta Phuoc Loc
Affiliation:
Laboratoire d'Informatique pour la Mécanique et les Sciences de l'Ingénieur, 91403 Orsay Cedex, France
Annie Dulieu
Affiliation:
Laboratoire d'Informatique pour la Mécanique et les Sciences de l'Ingénieur, 91403 Orsay Cedex, France
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Abstract

The starting flows past a two-dimensional oscillating and translating airfoil are investigated by visualization experiments and numerical calculations. The airfoil, elliptic in cross-section, is set in motion impulsively and subjected simultaneously to a steady translation and a harmonic oscillation in pitch. The incidence of the airfoil is variable between 0° and 45° and the Reynolds number based on the chord length is between 1500 and 10000. The main object of the present study is to reveal some marked characteristics of the unsteady vortices produced from the oscillating airfoil set at large incidences in excess of the static stall angle. Another purpose is to examine, in some detail, the respective and combined effects of the major experimental parameters on the vortex wake development. It is shown that, in general, the dominant parameter of the flow is the reduced frequency not only when the airfoil oscillates at incidences close to the static stall angle but also at larger incidences. It is also demonstrated that, as the pitching frequency is increased, the patterns of the vortex wake are dependent on the product of the reduced frequency and the amplitude rather than on the frequency itself. It is noted that the combined effect of a high reduced frequency and a large amplitude can give rise to cyclic superposition of leading-edge vortices from which a gradually expanding standing vortex is developed on the upper surface.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 211 , February 1990 , pp. 37 - 60
Copyright
© 1990 Cambridge University Press

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