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Daneshfaraz R, Najibi72 A. Experimental Investigation of Hydraulic Jump in Sudden Contraction with Rough Bed. MCEJ 2022; 22 (6) :65-77
URL: http://mcej.modares.ac.ir/article-16-55462-en.html

One of the most important problems in downstream hydraulic structures is the destructive kinetic energy of the flow. Experts always try to properly design and reduce the effect of this destructive force on the downstream of hydraulic structures in rectangular channel. The aim of this study was to investigate the effect of sudden contraction with the rough bed of contracted section on the relative energy dissipation in the supercritical flow. Three types of constrictions with widths of 5, 10 and 15 cm and three roughnesses with average diameters of D₅₀=0.8, 1.28 and 2.08 cm and range of Froude number 2.5 to 7.5 and relative contracting 0.5 to 0.83 was examined. Experimental results showed that with increasing the upstream Froude number, the upstream relative energy dissipation (ΔE/E_A) increases. Also, by applying roughness to the bed of all three sections of contracting, it was observed that energy dissipation increased significantly so that the highest energy dissipation with 78.35% increase related to 15 cm contracting and the lowest energy dissipation with 43.35% increase related to the contracting of 5 cm. The relationships extracted to estimate the relative energy dissipation showed that the results are in good agreement with the experimental data with a correlation coefficient of 0.927 and a normalized square absorption line of 0.02.