Effect of sudden canal contraction on the discharge coefficient and the energy dissipation coefficient of the elliptical LOPAC gate*

Abstract

AbstractGates are usually made with a width smaller than the width of the canal to reduce construction and operation costs. In this study, the effect of a sudden contraction of the canal cross‐section on the hydraulic performance of the elliptical LOPAC (EL) gate was investigated in vitro. To that end, 108 experiments were carried out at three different flow discharges (25, 35, and 45 L/s), four different gate widths or sudden canal contractions (b = 50, 60, 70, and 80 cm), three different submergence ratios (Yt/Yu = 0.7, 0.8, and 0.9), and three different gate‐closing angles (15, 20, and 25). For this purpose, using the discharge coefficient and energy dissipation coefficient, distinct equations were obtained to estimate the discharge of the EL gate. By presenting an empirical relation, the discharge coefficient was estimated with a maximum error of ±9%. Experimental results showed that due to the sudden canal contraction, the discharge coefficient of the gate indicates a decrease of about 14%–73%. The energy drop coefficient for the EL gate was obtained based on experimental data. The energy dissipation coefficient was calculated to be 1.3 for the velocity head at the output of the EL gate, which estimated the discharge with a maximum error of ±11%.