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Low Reynolds number flow over a plane symmetric sudden expansion

Published online by Cambridge University Press:  29 March 2006

F. Durst ,
A. Melling  and
J. H. Whitelaw
F. Durst
Affiliation:
Department of Mechanical Engineering, Imperial College, London Present address: Sonderforsehungsbereieh 80, University of Karlsruhe, Germany.
A. Melling
Affiliation:
Department of Mechanical Engineering, Imperial College, London
J. H. Whitelaw
Affiliation:
Department of Mechanical Engineering, Imperial College, London
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Abstract

Flow visualization and laser-anemometry measurements are reported in the flow downstream of a plane 3: 1 symmetric expansion in a duct with an aspect ratio of 9·2: 1 downstream of the expansion. The flow was found to be markedly dependent on Reynolds number, and strongly three-dimensional even well away from the channel corners except at the lowest measurable velocities. The measurements at a Reynolds number of 56 indicated that the separation regions behind each step were of equal length. Symmetric velocity profiles existed from the expansion to a fully developed, parabolic profile far downstream, although there were substantial three-dimensional effects in the vicinity of the separation regions. The velocity profiles were in good agreement with those obtained by solving the two-dimensional momentum equation. At a Reynolds number of 114, the two separation regions were of different lengths, leading to asymmetric velocity profiles; three dimensional effects were much more pronounced. At a Reynolds number of 252, a third separation zone was found on one wall, downstream of the smaller of the two separation zones adjacent to the steps. As at the lower Reynolds numbers, the flow was very stable. At higher Reynolds numbers the flow became less stable and periodicity became increasingly important in the main stream; this was accompanied by a highly disturbed fluid motion in the separation zones, as the flow tended towards turbulence.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 64 , Issue 1 , 3 June 1974 , pp. 111 - 128
Copyright
© 1974 Cambridge University Press

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References

Abbott, D. E. & Kline S. J.1962 Experimental investigation of subsonic turbulent flow over single and double backward facing steps. J. Basic Engng, Trans. A.S.M.E. D 84, 317.Google Scholar
Back, L. H. & Roschke E. J.1972 Shear-layer flow regimes and wave instabilities and reattachment lengths downstream of an abrupt circular channel expansion. J. Appl. Mech., Trans. A.S.M.E., 94, 677.Google Scholar
Browand F. K.1966 An experimental investigation of the instability of an incompressible, separated shear layer. J. Fluid Mech., 26, 281.Google Scholar
Durst F., Melling, A. & Whitelaw J. H.1972 Optical anemometer measurements in recirculating flows and flames. Fluid Dynamic Measurements in the Industrial and Medical Environments. Proc. DISA Conf., vol. 1, paper 11. 2-2. Leicester University Press.
Gosman A. D., Pun W. M., Runchal A. K., Spalding, D. B. & Wolfshtein M.1969 Heat and Mass Transfer in Recirculating Flows. Academic.
Hung, T. K. & Macacno E. O.1966 Laminar eddies in a two-dimensional conduit expansion. Houille Blanche, 4, 391.Google Scholar
Iribarne A., Frantisak F., Hummel, R. L. & Smith J. W.1972 An experimental study of instabilities and other flow properties of alaminar pipe jet. A.1.Ch.E. J., 18, 689.Google Scholar
Macagno, E. O. & Hung, T. K. 1967 Computational and experimental study of a captive annular eddy. J. Fluid Mech., 28, 43.Google Scholar
Roberts L. W.1972 Turbulent swirling flows with recirculation. Ph.D. thesis, University of London.
Sato H.1956 Experimental investigation on the transition of laminar separated flow. J. Phys. Soc. Japan, 11, 702.Google Scholar
Sato H.1959 Further investigation on the transition of two-dimensional separated layer at subsonic speeds. J. Phys. Soc. Japan, 14, 1797.Google Scholar
Zemanick, P. P. & Dougall R. S.1970 Local heat transfer downstream of an abrupt circular channel expansion. J. Heat Transfer, Trans. A.S.M.E. C 92, 53.Google Scholar