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Flow patterns for an annular flow over an axisymmetric suddenexpansion

Published online by Cambridge University Press:  10 November 1997

H. J. SHEEN ,
W. J. CHEN  and
J. S. WU
H. J. SHEEN
Affiliation:
Institute of Applied Mechanics, National Taiwan University, Taipei 10764, Taiwan; e-mail: [email protected]
W. J. CHEN
Affiliation:
Institute of Applied Mechanics, National Taiwan University, Taipei 10764, Taiwan; e-mail: [email protected]
J. S. WU
Affiliation:
Institute of Applied Mechanics, National Taiwan University, Taipei 10764, Taiwan; e-mail: [email protected]
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Abstract

In this paper, an experimental investigation is described for a concentric annular flowover an axisymmetric sudden expansion by using both flow visualization and laser-Doppleranemometry (LDA) techniques. Depending upon the value of the Reynolds number and whether theReynolds number was increased or decreased, four typical flow patterns were classifiedaccording to the characteristics of the central and corner recirculation zones. The flowpatterns are open annular flow, closed annular flow, vortex shedding, and stable centralflow. Bifurcation for this flow occurred when 230 < Re < 440, whichwas verified by observing the variation of the reattachment length. The spatial growth ofvelocity fluctuations from the measurements demonstrated a tendency that shedding vorticesbehind the centrebody more strongly affect the reattachment length than flows without acentrebody.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 350 , 10 November 1997 , pp. 177 - 188
Copyright
© 1997 Cambridge University Press

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