Channel Slope Effect on Energy Dissipation of Flow over Broad Crested Weirs
- 1 Department of Civil Engineering, Al-Mustansiriayah University, Baghdad, Iraq
- 2 Lulea University of Technology, Lulea, Sweden
- 3 Department of Civil Engineering, Al-Mustansiriayah University, Baghdad, Iraq
- 4 Lulea University of Technology, Lulea, Sweden
Abstract
The main purpose of broad crested weir used in open channels is to raise and control upstream (U/S) water level. In this study, a new performance was added to this weir, by making a step at downstream (D/S) of weir. The energy dissipation, the height of the weir/the upstream water height ratio and Froude number relationships (E% – P/h – Fr) for three range of flume slop S = 0.0, 0.002 and 0.004 were simulated. The experiments were performed in a laboratory horizontal channel of 4.6 m length, 0.3 m width and 0.3 m depth for a wide range of discharge. The D/S step height of the weir was 7.5 cm. FLUENT software was used as numerical model which represent a type of Computational Fluid Dynamics (CFD) model in order to simulate flow over weirs. The Volume of Fluid (VOF) method with the Standard k – ε turbulence model was used to estimate the free surface profile and the structured mesh with high concentration near the wall regions. The experimental results of the water surface profile gave a high agreement with the results of the numerical models. The maximum value 28.78 of E% was obtained in single step broad crested weir in the experimental result and 27.35 in numerical result at S = 0.004. Finally, the range of the relative error of the energy dissipation between experimental and numerical results was achieved and the maximum was 6.76 in all runs.
- Chow, V.T. (1959) Open Channel Hydraulics. McGraw-Hill, New York.
- Chanson, H. (2001) Hydraulic Design of Stepped Spillways and Downstream Energy Dissipaters. Dam Engineering, 11, 205-242.
- Ramamurthy, A.S., Tim, U.S. and Rao, M.J. (1988) Characteristics of Square-Edged and Round-Nosed Broad-Crested Weirs. Journal of Irrigation and Drainage Engineering, 114, 61-73. https://doi.org/10.1061/(ASCE)0733-9437(1988)114:1(61)
- Hussein, H.H., Juma, A. and Shareef, S. (2009) Flow Characteristics and Energy Dissipation over Stepped Round-Nosed Broad-Crested Weirs. Al-Rafidain Engineering Journal, 17, 95-107.
- Al-Talib J. (2007) .Laboratory Study of Flow Energy Dissipation Using Stepped Weirs. M.Sc. Dissertation, University of Mosul, Mosul.
- Shahad E. (2012) Effect of Channel Slope on Energy Dissipation of Flow for Single Step Broad-Crested Weirs. Journal of Engineering and Development, 16, 91-103.
- Hamid, H., Inam, A.K. and Saleh, J.S. (2010) Improving the Hydraulic Performance of Single Step Broad-Crested Weirs. Journal of Civil Engineering, 7, 1-12.
- Yazdi, J., Sarkardeh, H., Azamathulla, H.M. and Ghani, A.A. (2010) 3D Simulation of Flow around a Single Spur Dike with Free Surface Flow. International Journal of River Basin Management, 8, 55-62. https://doi.org/10.1080/15715121003715107
- Sarkar, M.A. and Rhodes. D.G. (2004) CFD and Physical Modeling of Free Surface over Broad-Crested Weir. Cranfield University, Cranfield.
- Gonzalez, C.A. and Chanson, H. (2007) Experimental Measurements of Velocity and Pressure Distribution on a Large Broad-Crested Weir. Journal of Flow Measurement and Instrumentation, 18, 107-113. https://doi.org/10.1016/j.flowmeasinst.2007.05.005
- Hargreaves, D.M., Morvan, H.P. and Wright, N.G. (2007) Validation of the Volume of Fluid Method for Free Surface Calculation: The Broad-Crested Weir. Engineering Applications of Computational Fluid Mechanics, 1, 136-146. https://doi.org/10.1080/19942060.2007.11015188
- Hager, W.H. and Schwalt, M. (1994) Broad-Crested Weir. Journal of Irrigation and Drainage Engineering, 120, 13-26. https://doi.org/10.1061/(ASCE)0733-9437(1994)120:1(13)
- Afshar, H. and Hooman, H. (2013) Experimental and 3-D Numerical Simulation of Flow over a Rectangular Broad-Crested Weir. International Journal Engineering and Advanced Technology, 2, 214-219.