Calculation of contraction coefficient under sluice gates and application to discharge measurement

The contraction coefficient under sluice gates on flat beds is studied for both free flow and submerged conditions based on the principle of momentum conservation, relying on an analytical determination of the pressure force exerted on the upstream face of the gate together with the energy equation. The contraction coefficient varies with the relative gate opening and the relative submergence, especially at large gate openings. The contraction coefficient may be similar in submerged flow and free flow at small openings but not at large openings, as shown by some experimental results. An application to discharge measurement is also presented. DOI: 10.1061/(ASCE)HY. 1943-7900.0000122 CE Database subject headings: Gates; Contraction: Coefficients; Hydraulic structures; Potential flow; Submerged flow; Free flow; Discharge measurement.