Experimental Study of Flow Characteristics in Wedge and Modified Wedge Transitions
Publication: Journal of Hydraulic Engineering
Volume 144, Issue 8
Abstract
Water generally leaves a supply reservoir through a narrow rectangular concrete channel and enters a large trapezoidal earthen channel. The two channels are connected by a transition. Among the most common types of transitions, a wedge transition is relatively simple to construct. Even in well-designed transitions, the flow is often accompanied by a large zone of flow separation, causing considerable head loss. For the first time, this experimental study has explored modifications to a wedge transition to reduce the separation and head loss. The characteristics of three-dimensional flow in both the wedge and the modified wedge systems were investigated using non-intrusive measurements of the flow field. Transition flow parameters, including longitudinal flow profile, transition energy loss, maximum velocity at the transition outlet, and turbulence intensity in the downstream trapezoidal channel, were determined. Flow separation characteristics were recorded by tracing the separation zone and the points of reattachment based on velocity data, and were confirmed by visual observation involving dye tests. For both systems, separation occurred on one side and the flow was three dimensional. Compared with the wedge transition, the modified wedge transition effectively guides the flow and prevents abrupt changes in flow direction. The modified wedge transition results in a much earlier recovery of the flow in the downstream channel, lower levels of turbulence, and a less strong secondary flow. It also achieves a small gain in the energy at the flow recovery location and reduces the head loss coefficient as a result of the reduced separation zone.
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Acknowledgments
This paper receives financial support from the National Sciences and Engineering Research Council of Canada through Discovery Grants held by S. Samuel Li.
References
Abbott, D. E., and S. J. Kline. 1962. “Experimental investigation of subsonic turbulent flow over single and double backward facing steps.” J. Basic Eng. 84 (3): 317–325. https://doi.org/10.1115/1.3657313.
Alauddin, M., and B. C. Basak. 2006. “Development of an expansion transition in open channel subcritical flow.” J. Civ. Eng. 34 (2): 91–101.
Alouri, F., and M. Souhar. 2000. “Experimental study of turbulent asymmetric flow in a flat duct symmetric sudden expansion.” J. Fluids Eng. 122 (1): 174–177. https://doi.org/10.1115/1.483245.
Asnaashari, A., A. A. Akhtari, A. A. Dehghani, and H. Bonakdari. 2016. “Experimental and numerical investigation of the flow field in the gradual transition of rectangular to trapezoidal open channels.” Eng. Appl. Comput. Fluid Mech. 10 (1): 272–282. https://doi.org/10.1080/19942060.2016.1149102.
Basak, B. C., and M. Alauddin. 2010. “Efficiency of an expansive transition in an open channel subcritical flow.” DUET J. 1 (1): 27–32.
Brundrett, E., and W. D. Baines 1964. “The production and diffusion of vorticity in duct flow.” J. Fluid Mech. 19 (3): 375–394. https://doi.org/10.1017/S0022112064000799.
Chaturvedi, R. S. 1963. “Expansive subcritical flow in open channel transitions.” J. Inst. Eng. 43 (9): 447–487.
Chow, V. T. 1959. Open-channel hydraulics. New York, NY: McGraw-Hill.
Education Development Center. 1972. “National committee for fluid mechanics films: Flow visualization.” Accessed December 2, 2017. http://web.mit.edu/hml/ncfmf.html.
El-Shewey, M. I. A., and S. G. Joshi. 1996. “A study of turbulence characteristics in open channel transitions as a function of Froude and Reynolds numbers using laser technique.” Adv. Fluid Mech. 9: 363–372.
Formica, G. 1955. “Esperienze preliminary sulle predate di carcico nei caneli, dovute a combiamenti di sezione [Preliminary test on head losses in channel due to cross-sectional changes].” L’Energia Electrica 32 (7): 554–568.
Fox, R. W., P. J. Pritchard, and A. T. McDonald. 2009. Introduction to fluid mechanics. 7th ed. Hoboken, NJ: Wiley.
Han, S. S., A. S. Ramamurthy, and P. M. Biron. 2011. “Characteristics of flow around open channel 90° bends with vanes.” J. Irrig. Drain. Eng. 137 (10): 668–676. https://doi.org/10.1061/(ASCE)IR.1943-4774.0000337.
Haque, A. 2008. “Some characteristics of open channel transition flow.” M.A.Sc. thesis, Dept. of Building, Civil and Environmental Engineering, Concordia Univ.
Henderson, F. M. 1966. Open channel flow. Upper Saddle River, NJ: Prentice-Hall.
Hinds, J. 1928. “The hydraulic design of flume and siphon transitions.” Trans. ASCE 92 (1): 1433–1459.
Ippen, A. T. 1949. “Channel transitions and controls.” In Engineering Hydraulics: Proc., 4th Hydraulics Conf., 496–588. New York, NY: Wiley.
Isbash, S. V., and I. V. Lebedev. 1961. “Change of natural streams during construction of hydraulic structures.” In Proc., 9th Congress of IAHR, 1114–1121. Belgrade, Yugoslavia: Yugoslav Association for Hydraulic Research.
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.
Mitra, A. C. 1940. Report on the model experiments of fluming of bridges on Purva branch. Roorkee, India: United Provinces Irrigation.
Morris, H. M., and J. M. Wiggert. 1972. Applied hydraulics in engineering. 2nd ed. New York: The Ronald Press.
Najafi-Nejad-Nasser, A., and S. S. Li. 2015. “Reduction of flow separation and energy head losses in expansions using a hump.” J. Irrig. Drain. Eng. 141 (3): 04014057. https://doi.org/10.1061/(ASCE)IR.1943-4774.0000803.
Papanicolaou, A., and R. Hilldale. 2002. “Turbulence characteristics in a gradual channel transition.” J. Eng. Mech. 128 (9): 948–960. https://doi.org/10.1061/(ASCE)0733-9399(2002)128:9(948).
Ramamurthy, A. S., S. Basak, and P. R. Rao. 1970. “Open channel expansions fitted with local hump.” J. Hydraul. Div. 96 (HY5): 1105–1113.
Ramamurthy, A. S., D. R. Thapa, and S. S. Li. 2017. “Experimental study of flow past a warped transition.” J. Irrig. Drain. Eng. 143 (8): 04017022. https://doi.org/10.1061/(ASCE)IR.1943-4774.0001200.
Scobey, F. C. 1933. The flow of waters in flumes,. Washington, DC: US Dept. of Agriculture.
Simmons, W. P. Jr. 1964. Hydraulic design of transitions for small canals. Engineering Monograph No. 33. Denver: US Dept. of the Interior, Bureau of Reclamation.
Smith, C. D., and J. N. G. Yu. 1966. “Use of baffles in open channel expansions.” J. Hydraul. Div. 92 (HY2): 1–17.
Swamee, P. K., and B. C. Basak. 1991. “Design of rectangular open-channel expansion transitions.” J. Irrig. Drain. Eng. 117 (6): 827–838. https://doi.org/10.1061/(ASCE)0733-9437(1991)117:6(827).
Swamee, P. K., and B. C. Basak. 1992. “Design of trapezoidal expansive transitions.” J. Irrig. Drain. Eng. 118 (1): 61–73. https://doi.org/10.1061/(ASCE)0733-9437(1992)118:1(61).
Swamee, P. K., and B. C. Basak. 1993. “Comprehensive open-channel expansion transition design.” J. Irrig. Drain. Eng. 119 (1): 1–17. https://doi.org/10.1061/(ASCE)0733-9437(1993)119:1(1).
Vittal, N., and V. V. Chiranjeevi. 1983. “Open channel transitions: Rational method of design.” J. Irrig. Drain. Eng. 109 (1): 99–115. https://doi.org/10.1061/(ASCE)0733-9429(1983)109:1(99).
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Published In
Journal of Hydraulic Engineering
Volume 144 • Issue 8 • August 2018
Copyright
©2018 American Society of Civil Engineers.
History
Received: Dec 20, 2017
Accepted: Feb 2, 2018
Published online: May 21, 2018
Published in print: Aug 1, 2018
Discussion open until: Oct 21, 2018
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