Hydraulic characteristics of a sluice gate over a broad-crested weir

Abstract

Vertical sluice gates are commonly used to control and measure flow in irrigation and drainage networks. To reduce their size and associated maintenance and operation costs, they are sometimes installed above broad-crested weirs. To explore the effects of the installation location of the sluice gate and the sill height on the hydrodynamic characteristics of the flow passing through the sluice-gated weir, six laboratory models were tested. The 427 and 449 data points included both free- and submerged-flow conditions, respectively. Analytical relationships were developed for the contraction, head-loss, and Henry's (1950) discharge coefficients. Based on the maximization of the discharge and contraction coefficients and the minimization of the head-loss coefficient, results suggest that a gate should be installed at a distance of L/2 (where L is the sill length) from the upstream end of the weir crest, and the height of 1.25Hd (where Hd is the water depth as referenced from the weir sill elevation) is the optimal height for the weir. By conducting experiments and constructing correlations for determining the contraction and head-loss coefficients under free flow conditions, the average values of these coefficients for the laboratory models were obtained as 0.664 and 0.133, respectively. Applying the average contraction and head-loss coefficients to the developed relationship for estimating the free and submerged discharge coefficients resulted in an error of 4% and 6%, respectively. WinGate alpha 0.2 software was used to estimate the experimental free and submerged discharge coefficient of the gated weir with an average error of 5.4% and 12.7%, respectively. It was done without any consideration of the cross-section shape of the weir or the location of the gate on the weir sill. In addition, an inspection of the submergence threshold of the gated weir showed an increase in the submergence threshold when the gate was moved further downstream from the upstream end of the sill.