Analysis of the Discharge and Flow Conditions in Sluice-Gated Spillways

Sluice gates are designed and used in Ogee spillways with high height (regulator dams) or low height (as sill) for better controlling the flow. In latter case, according to different combinations of weir geometry, gate opening, upstream and downstream flow depths, four different flow conditions are recognizable: (a) free uncontrolled flow, (b) submerged uncontrolled flow, (c) free controlled flow, and (d) submerged controlled flow. Determination of change threshold of these flow condition is useful for choosing the proposed discharge equations in any situation. In current research, using the experimental data gathered from two Ogee spillways with different height in this program and using the data gathered from typical spillway structures in central and southern Florida water-control project, different equations for determining the change threshold and flow discharge in four different flow conditions are developed. In free uncontrolled flow condition, the proposed discharge equation has an average relative error of 1.95% while in free and submerged controlled flow condition, the proposed discharge equations have the average relative errors of 2% and 5% respectively. Results showed that the change threshold of uncontrolled flow into controlled flow occurs when upstream flow depth increases about 1.46 times the gate opening. Furthermore, the relative submergence threshold and flow discharge increase by increasing the downstream flow depth and decreasing the upstream flow depth.