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Vorticity transport in the leading-edge vortex on a rotating blade

Published online by Cambridge University Press:  03 March 2014

Craig J. Wojcik
Affiliation:
Department of Mechanical and Industrial Engineering, University of Iowa, Iowa City, IA 52242, USA IIHR - Hydroscience and Engineering, Iowa City, IA 52242, USA
James H. J. Buchholz*
Affiliation:
Department of Mechanical and Industrial Engineering, University of Iowa, Iowa City, IA 52242, USA IIHR - Hydroscience and Engineering, Iowa City, IA 52242, USA
*
Email address for correspondence: [email protected]

Abstract

Vorticity transport is analysed within the leading-edge vortex generated on a rectangular flat plate of aspect ratio 4 undergoing a starting rotation motion in a quiescent fluid. Two analyses are conducted on the inboard half of the blade to better understand the vorticity transport mechanisms responsible for maintaining the quasi-equilibrium state of the leading-edge vortex. An initial global analysis between the $25$ and $50\, \%$ spanwise positions suggests that, although spanwise velocity is significant, spanwise convection of vorticity is insufficient to balance the flux of vorticity from the leading-edge shear layer. Subsequent detailed analyses of vorticity transport in planar control volumes at the $25$ and $50\, \%$ spanwise positions verify this conclusion and demonstrate that vorticity annihilation due to interaction between the leading-edge vortex and the opposite-sign layer on the plate surface is an important, often dominant, mechanism for regulation of leading-edge-vortex circulation. Thus, it provides an important condition for maintenance of an attached leading-edge vortex on the inboard portion of the blade.

Type
Papers
Copyright
© 2014 Cambridge University Press 

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