Department of Water Engineering, Faculty of Agriculture, University of Tabriz , salmasi@tabrizu.ac.ir
Abstract: (644 Views)
Sluice gates are commonly used to measure water discharge and to adjust the water level in open canals. Sluice gates can also be used at the crest of dam spillways for controlling floods. Estimation of head loss (∆E/E0) and discharge coefficients (Cd) for a sluice gate is essential for the design of open canals. Depending on the downstream water level, free or submerged flow conditions may occur. Although there have been some investigations on Cd for sluice gates, a comprehensive literature review shows that there are no studies of ∆E/E0 (to the best knowledge of the authors). Knowledge of ∆E/E0 is necessary for the design of intakes and irrigation canal inverts. This study uses the physical model of sluice gate to introduce helpful charts for energy loss estimation. Experiments were conducted in the University of Tabriz, department of water engineering. A rectangular canal with length of 12 m, width of 0.5 m and height of 0.8 m was used. Vertical slide gate was installed at the 6 m from canal inlet to permit flow become uniform. Water circulation is carried out using a submerged pump. Water is pumped in a 4.5 m head tank and then inters to canal with pipes. Water level/depth was measured with a point gauge with 0.1 mm accuracy. Discharge was measured with a calibrated rectangular sharp crested weir. Experiments were carried out with different discharges and gate opening. Results show that ∆E for free flow is greater than that for submerged flow conditions. Meanwhile, discharge coefficients in a free flow are greater than those under submerged flow conditions. Relative energy losses (∆E/E0) have a minimum value of 0.271 and a maximum value of 0.604. These high energy losses cannot be ignored in intake structures and canal-designing processes and their impact on minor canal inverts receiving water from main canals should be considered. The relative energy loss changed from the minimum value of 0.271 to the maximum value of 0.604. Multivariate regression method was used to calculate the relative energy loss and the average of the residuals was -0.004. The maximum and minimum residuals for ∆E/E0 are 5 and -0.31, respectively. A mathematical equation with a coefficient of determination of 0.925 was presented to separate the boundary of free flow from submerged flow. To estimate the discharge coefficient in submerged flow, a mathematical equation was obtained. For this equation, the average of the residuals was -0.004. The maximum and minimum residuals for the discharge coefficient are -0.084 and 0.116, respectively. Application of multiple non-linear regression (MNR) models are presented for predicting ∆E/E0 and Cd. The high energy losses cannot be ignored in intake structures and canal designing processes. Their impact on minor canal inverts receiving water from main canals should be considered. Application of MNR was presented from a simple equation to more sophisticated equations by improving regression relations in each step. The MNR method provides accurate equations for predicting performance for both ∆E and Cd.
Keywords: Head loss, Sluice gate, Multiple non-linear regression, Submerged flow, Discharge coefficient
Article Type: Original Research |
Subject:
Hydraulical Structures
Received: 2024/07/8 | Accepted: 2024/11/24
Received: 2024/07/8 | Accepted: 2024/11/24
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