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Topological Flow Structures of Annular Swirling Jets

Published online by Cambridge University Press:  05 May 2011

Feng Chin Tsai  and
Rong Fung Huang
Feng Chin Tsai*
Affiliation:
Department of Mechanical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan 10672, R.O.C.
Rong Fung Huang*
Affiliation:
Department of Mechanical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan 10672, R.O.C.
*
*Graduate student
**Professor
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Abstract

The effects of blockage and swirl on the macro flow structures of the annular jet past a circular disc are experimentally studied through the time-averaged streamline patterns. In the blockage-effect regime, the flows present multiple modes, single bubble, dual rings, vortex breakdown, and triple rings, in different regimes of blockage ratio and swirl number. The topological models of the flow structures are proposed and discussed according to the measured flow fields to manifest the complex flow structures. The single bubble is a closed recirculation bubble with a stagnation point on the central axis. The dual-ring flow is an open-top recirculsation zone, in which a pair of counter-rotating vortex rings exists in the near wake. The fluids in the dual rings are expelled downstream through a central jet-like swirling flow. A vortex breakdown may occur in the central jet-like swirling flow if the exit swirl number exceeds critical values. When the vortex breakdown interacts with the dual rings, a complex triple-ring flow structure forms. Axial distributions of the local swirl number are presented and discussed. The local swirl number increases with the increase of the exit swirl number and attains the maximum in the dual-ring mode. At large exit swirl numbers where the vortex breakdown occurs, the local swirl number decreases drastically to a low value.

Keywords

Swirling wakeVortex breakdownRecirculation bubble
Type
Articles
Information
Journal of Mechanics , Volume 17 , Issue 3 , September 2001 , pp. 131 - 138
Copyright
Copyright © The Society of Theoretical and Applied Mechanics, R.O.C. 2001

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