Experimental Study Discharge Coefficient of Proportional Weirs on Lateral Intake

Document Type : پژوهشی

Authors

• Javad Ghaffari Gousheh ¹
• Rouhallah Fatahi Nafchi ²
• Hosein Samadi Borojeni ²

¹ Department of Water Engineering, Shahre_kord University, Shahre_kord ,Iran.

² Department of water engineering, Shahre_kord University, Shahre_kord ,Iran.

10.22067/jfcei.2021.60900.0

Abstract

Accurate measurement of flow discharge in open channel and water and sewage transmission networks it is of special importance. So far, various types of structures, such as overflows, stomata, flumes and sliding valves, have been proposed for measuring current flow. The proportional weirs are a group of sharp edges weirs that are highly accurate due to low sensitivity to upstream depth variations. In linear proportional weirs, there is a linear relationship between the head and the discharge. In this study, based on theoretical fundamentals of proportional weirs, three proportional linear weirs with linear, triangular and reverse triangular, and two reverse triangles and three series of rectangular weirs were designed and tested in rectangular flume equipped with a side channel in hydraulic lab. About 400 laboratory experiments were carried out lead to, establish a linear relationship between the head and the discharge in linear proportional weirs based on the measurements. The range of the studied discharges varied from 2 to 16 liters per second. The experiments showed that the coefficient of discharge is as a function of two ratios, which are the water depth at the top of the weir and the length of the crest to the height of the weir. Based on these ratios, for each weir a relationship for the discharge coefficient was determined. The average error for proposed equation for linear correlation weirs was equal to 1.5 percent and for over 90 percent of laboratory data the average errors were less than this value. The results show that theoretical sensitivity in linear proportional weirs is equals to one, the more the values of the sensitivity of the studied weir are close to the theoretical values, the better the weir will be. In order to estimate the laboratory sensitivity of the above weirs, the derived relationship between the discharge and head of each weirs was used and compared. The results showed that among linear proportional weirs, inverse triangular weir with a linear relationship, ­has better and more accurate hydraulic performance.

Keywords

• linear proportional weir
• Discharge coefficient
• Lateral intake
• Rectangular Channel

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References

1. Keshava Murthy, K., and Giridhar, D. P., "Inverted v-notch: Practical proportional weir", Journal of irrigation and drainage engineering, Vol. 115, No.6, pp. 1035-1050, (1989).
2. Bos, M.G., "Discharge measurement structures", 2^nd ed. 464 pp. Publication 20, International Institute for Land Reclamation and Improvement (ILRI), Wageningen, The Netherlands, pp. 17-38 (1978).
3. Keshava Murthy, K., and Pillai, K. G., "Design of constant accuracy linear proportional weir", Journal of the Hydraulics Division, Vol. 104, No.4, pp. 527-541, (1978).
4. Keshava Murthy, K., and Pillai, K. G., "Modified proportional V-notch weirs", Journal of the Hydraulics Division, Vol. 104, No.5, pp. 775-791, (1978).
5. Stout, O. V. P., " A new form of weir notch", Transaction Nebraska Engineering Society, Vol. 13, No.1, pp 18-24, (1897).
6. Baddour, R. E., "Head-discharge equation for sharp-crested polynomial weir", Journal of Irrigation and Drainage Engineering, Vol. 134, No.2, pp. 260-262, (2008).
7. Troskolanski, A. T., "Hydrometry;: Theory and practice of hydraulic measurements", Pergamon Press, 648 pages ( 1960).
8. Keshava Murthy, K., and Giridhar, D. P., "Improved inverted V-notch or chimney weir", Journal of irrigation and drainage engineering, Vol. 116, No.3, pp. 374-386, (1990).
9. Swamee, P. K., Pathak, S. K., Agarwal, M., and Ansari, A. S., "Alternative linear weir design", Journal of irrigation and drainage engineering, Vol. 117, No.3, pp. 311-323, (1991).
10. Vatankhah, A. R., and Kouchakzadeh, S., "Discussion of Head-discharge equation for sharpcrested polynomial weir", by Baddour, R.E. Journal of Irrigation and Drainage Engineering, Vol. 135, No.3, pp. 393-395, (2009).
11. Vatankhah, A. R., "Head-Discharge Equation for Sharp Crested Weir with Piecewise-Linear Sides", Journal of Irrigation and Drainage Engineering, Vol. 138, No.11, pp. 1011-1018, (2012).
12. Aslani, N., Ebrahim, T., Vatankhah, A. R., "Experimental Study of Linear And Logarithmic Proportional Weir In Rectangular Channels", Journal of Hydraulic Research, Vol. 8, No.4, pp. 43-53, (2014).