The effect of upstream and downstream bed level on discharge coefficient of duckbill sharp-crested weir | ||
| مهندسی و مدیریت آبخیز | ||
| Article 4, Volume 9, Issue 4, January 2018, Pages 413-425 PDF (962.58 K) | ||
| Document Type: Research Paper | ||
| DOI: 10.22092/ijwmse.2017.113461 | ||
| Authors | ||
| Davoud Davoudmaghami* 1; Hossein Banejad2; Mojtaba Saneie3; Seyyed Asadollah Mohseni Movahhed4 | ||
| 1PhD Student of Water Engineering, Agricultural College, Buali Sina University, Hamedan, Iran | ||
| 2Associate Professor, Department of Water Engineering, Agricultural College, Buali Sina University, Hamedan, Iran | ||
| 3Associate Professor, Soil Conservation and Watershed Management Research Institute, Agricultural Research, Education and Extension Organization (AREEO), Tehran, Iran | ||
| 4Assistant Professor, Department of Water Engineering, Agricultural College, Arak University, Arak, Iran | ||
| Abstract | ||
| Sharp-crested weirs are widely used for the purposes of flow measurement, flow diversion and water level control in hydraulics, irrigation, and environmental projects. Discharge coefficient at these weirs is a function of head to weir height ratio (H/P). In a constant head, flow increases by increasing the length of weir in the plan. One of these weirs is the duckbill weir. Sometimes, it is changed upstream and downstream bed level by deposition of sediments in the upstream of weir, erosion in the downstream of the weir, etc. These changes cause changes in the flow characteristics such as discharge coefficient. In this study, the effect of these changes on the discharge coefficient of duckbill weir is studied. The results showed that the change in the height of duckbill weir has no effect on the discharge coefficient. But, increasing L/W ratio (L and W are respectively length of weir and width of flume) decreases discharge coefficient. Also, with increasing, maximum of discharge coefficient gives in the amount of H/P less. So that maximum of discharge coefficient in L/W ratio 2, 3 and 4 is respectively 0.73, 0.68 and 0.63 which respectively occurred in the amount of H/P of 0.5, 0.3 and 0.25. Discharge coefficient is reduced with increasing upstream bed level. In submerged flow, Reducing the downstream bed level increase discharge coefficient but changes in downstream bed level have no effect on discharge coefficient until flow is not submerged, also, conditions of aeration are the same. By increasing the L/W ratio in duckbill weir from 3 to 4, amount of H/P in threshold of flow Interference and local Submergence decreased from 0.5 to 0.3. | ||
| Keywords | ||
| Discharge capacity; Head to weir height ratio (H/P); L/W ratio; Nonlinear weir; Submerged flow | ||
| References | ||
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