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

Abstract

Gates 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 (Y t /Y u = 0.7, 0.8, and 0.9), and three different gateclosing 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%. K E Y W O R D S discharge coefficient, elliptical LOPAC gate, energy dissipation coefficient Résumé Les vannes sont généralement fabriquées avec une largeur inférieure à la largeur du canal pour réduire les coûts de construction et d'exploitation. Dans cette étude, l'effet d'une contraction soudaine de la section transversale du canal sur les performances hydrauliques de la vanne elliptique LOPAC (EL) a été étudié in vitro. À cette fin, 108 expériences ont été menées à trois débits différents (25, 35 et 45 L/s), quatre largeurs de grille différentes ou des contractions brusques de canal (b = 50, 60, 70 et 80 cm), trois rapports de submersions différents (Y t /Y u = 0,7, 0,8 et 0,9) et trois angles d'ouverture de vanne différents (15, 20 et 25). Pour cela, en utilisant le coefficient de débit et le coefficient de dissipation d'énergie, des équations distinctes ont été obtenues * Effet de la contraction soudaine du canal sur le coefficient de débit et le coefficient de dissipation d'énergie de la vanne elliptique-LOPAC

Investigation of the Different Models of Elliptical-Lopac Gate Performance under Submerged Flow Conditions

“…Shafai Bejestan et al (2020) measured the discharge coefficient associated to the opening of an elliptical Lopac gate gradually converging to the center of channel. Kheybar et al (2021) used in a laboratory flume a compound structure obtained by installing the Lopac gate at the end of a sudden contraction, made by a short wall orthogonal to the bank. The effects of the presence of the sudden contraction on the discharge coefficient and on energy dissipation have been measured in a set of different opening angles of the Lopac gate, confirming trends already shown by Pilbala et al (2021) without the sudden contraction.…”