Experimental and Numerical Investigation of the Effect of Transition Length on Energy Losses in Gradual Transitions Open Channels Under Subcritical Flow

Document Type : Research Paper


1 Ph.D. Candidate of Civil Engineering, Hydraulic Structures, Razi University, Kermanshah, Iran.

2 Assistant Professor, Department of Civil Engineering, Razi University, Kermanshah, Iran

3 Associate Professor, Department of Water Engineering, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran.

4 4- Professor, Department of Civil Engineering, Razi University, Kermanshah, Iran.


'Transition' is a short hydraulic structure used to change the cross-sectional shape or flow shape. Transitions are commonly used both in the open-channels and natural waterways. The task of a transition is to connect a narrow channel at the upstream to a wider downstream channel or vice-versa. This, creates a disturbance region of turbulent flow causing energy losses. In general, the structure of a transition prevents the formation of wave and other turbulencies. In this case, the energy loss, due to the change in the amount of the momentum, will be minimized.


Main Subjects

1- Abbott, D. E., and S. J. Kline. 1962. Experimental investigation of subsonic turbulent flow over single and double backward facing steps. Journal of Basic Engineering 84, 317.
2- Alauddin, M., and B. C. Basak. 2006. Development of an Expansion Transition in Open Channel Sub-Critical Flow. Journal of Civil Engineering, 34(2): 91-101.
3- Basak, B. C., and M. Alauddin. 2010. Efficiency of an Expansive Transition in an Open Channel Subcritical Flow. DUET Journal., Dhaka University of Engineering & Technology: 27-32.
4- Fluent 6.3.26 User Manual, Fluent Inc, 2006.
5- Haque, A. 2008. Some Characteristics of Open Channel Transition Flow. Msc Thesis, Civil Engineering, Concordia University.
6- Henderson, F. M. 1966. Open Channel Flow. Prentice-Hall, Inc., Upper Saddle River, NJ 07458.
7- Hosseini, S. M., and J. Abrishami. 2014. Hydraulic open channels. Imam Reza University Publishers, Thirty-First Edition. (In Persian).
8- Howes, D. J., Burt, C. M. and B. F. Sanders. 2010. Subcritical contraction for improved open-channel flow measurement accuracy with an upward-looking ADVM. Journal of Irrigation and Drainage Engineering, 136: 617–626.
9- Najafi Nejad Nasser, A. 2011. An Experimental Investigation of Flow Energy Losses in Open- Channel Expansions, Msc Thesis, Civil Engineering, Concordia University.
10- Najmeddin, S. 2012. CFD Modeling of Turbulent Flow in Open-Channel Expansions. Msc Thesis, Civil Engineering, Concordia University.
11- Ramamurthy, A. S., Basak, S. and P. R. Rao. 1970. Open channel expansions fitted with local hump. Journal of hydraulics division, ASCE 96(HY5): 1105–1113.
12- Swamee, P. K. and B. C. Basak. 1992. Design of trapezoidal expansive transitions. Journal of Irrigation and Drainage Engineering, ASCE 118(1): 61-73.
Volume 41, Issue 2
June 2018
Pages 45-59
  • Receive Date: 02 January 2016
  • Revise Date: 20 November 2016
  • Accept Date: 04 December 2016
  • First Publish Date: 22 June 2018