Reduction of Flow Separation and Energy Head Losses in Expansions Using a Hump
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VIEW THE REPLYPublication: Journal of Irrigation and Drainage Engineering
Volume 141, Issue 3
Abstract
Irrigation channels need expansions to provide a cross-sectional transition. Expansions often cause flow separation, turbulent eddy motions, channel erosion, and flow energy dissipation. The purpose of this paper is to investigate the effectiveness of fitting a hump at the expansion’s bottom in reducing flow separation and energy loss. This paper reports analytical solutions to the problem of flow transition and associated energy head loss, by using the momentum and energy concepts complementarily, as well as experimental results for verifying the solutions. The use of a triangular hump can effectively reduce head loss; the head loss coefficient drops by a factor of up to 4. The mechanism at work is that the presence of a hump forces the flow to accelerate, neutralizes the decelerating effects of expanding width, and creates favorable pressure gradients working against flow separation. Humps with a crest height of 5–9% of the depth of approach flow are recommended, with a good potential to save a substantial amount of flow energy. Researchers can easily incorporate such humps into existing expansions.
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Acknowledgments
This paper receives financial support from the Natural Sciences and Engineering Research Council of Canada through Discovery Grants held by S. S. Li. The writers thank the reviewers for their helpful input.
References
Foumeny, E. A., Ingham, D. B., and Walker, A. J. (1996). “Bifurcations of incompressible flow through plane symmetric channel expansions.” Comput. Fluids, 25(3), 335–351.
Graber, S. D. (1982). “Asymmetric flow in symmetric expansions.” J. Hydraul. Div., 108(HY10), 1082–1101.
Henderson, F. M. (1966). Open channel flow, Prentice-Hall, Upper Saddle River, NJ.
Hinds, J. (1928). “The hydraulic design of flume and siphon transitions.” Trans. Am. Soc. Civ. Eng., 92(1), 1433–1459.
Mehta, P. R. (1979). “Flow characteristics in two-dimensional expansions.” J. Hydraul. Div., 105(HY5), 501–516.
Mehta, P. R. (1981). “Separated flow through large sudden expansions.” J. Hydraul. Div., 107(HY4), 451–460.
Nashta, C. F., and Garde, R. J. (1988). “Subcritical flow in rigid-bed open channel expansions.” J. Hydraul. Res., 26(1), 49–65.
Ramamurthy, A. S., Basak, S., and Rao, P. R. (1970). “Open channel expansions fitted with local hump.” J. Hydraul. Div., 96(HY5), 1105–1113.
Skogerboe, G. V., Austin, L. H., and Bennett, R. S. (1971). “Energy loss analysis for open channel expansions.” J. Hydraul. Div., 97(HY10), 1719–1736.
Smith, C. D., and Yu, J. N. G. (1966). “Use of baffles in open channel expansion.” J. Hydraul. Div., 92(HY2), 1–17.
Swamee, P. K., and Basak, B. C. (1991). “Design of rectangular open-channel expansion transitions.” J. Irrig. Drain. Eng., 827–838.
Swamee, P. K., and Basak, B. C. (1992). “Design of trapezoidal expansive transitions.” J. Irrig. Drain. Eng., 61–73.
Vittal, N., and Chiranjeevi, V. V. (1983). “Open channel transitions: Rational method of design.” J. Hydraul. Eng., 99–115.
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Journal of Irrigation and Drainage Engineering
Volume 141 • Issue 3 • March 2015
Copyright
© 2014 American Society of Civil Engineers.
History
Received: Mar 3, 2014
Accepted: Jul 15, 2014
Published online: Aug 20, 2014
Discussion open until: Jan 20, 2015
Published in print: Mar 1, 2015
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