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A numerical and experimental study of transition processes in an obstructed channel flow

Published online by Cambridge University Press:  26 April 2006

E. P. L. Roberts
E. P. L. Roberts
Affiliation:
Department of Chemical Engineering, University of Cambridge, Pembroke Street, Cambridge, CB2 3RA, UK Present address: EA Technology, Environmental Technology Division, Capenhurst, Chester, CH1 6ES, UK.
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Abstract

Incompressible Newtonian flow in a two-dimensional channel with periodically placed sharp edged baffles has been studied both by numerical simulation and by experimental flow visualization. The flow was observed to be steady and symmetric at low Reynolds numbers, with recirculating eddies downstream of each baffle. At a critical Reynolds number (based on channel width and cross-sectional mean velocity) of approximately 100 the flow became asymmetric and unsteady. This transition to unsteadiness led to an eddy shedding regime, with eddies formed and shed successively from each baffle. A stability study suggested that the mechanism for transition to unsteady flow is a Kelvin–Helmholtz instability associated with the shear layer formed downstream of the sharp edged baffles. The frequency of the unsteadiness is, however, dependent on the full flow field, and not only the shear layer characteristics. Experimental observations show that the instability is followed by a secondary transition to three-dimensional disordered flow. Experimentally observed flows in the two-dimensional regime were found to be in close agreement with the numerical simulation for both the steady and unsteady flows.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 260 , 10 February 1994 , pp. 185 - 209
Copyright
© 1994 Cambridge University Press

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