Experimental Study of Effect of Rough Bed on Sequent Depth Ratio of Hydraulic Jump on Adverse Slope

Abstract

Hydraulic jump is one of the important phenomena in rapidly varied flow. Due to this phenomenon the energy loss, the upstream flow velocity significantly decreases. In the present study, hydraulic jump on a new roughened bed -with half cylindrical shape bars with three heights (r) and four different longitudinal spacing (s=1D, 2D, 3D, 4D) were investigated. In total 238 experiments were performed for a range of Froude numbers from 4.6 to 7.4 on horizontal bed and two adverse slopes of 1 and 1.5 %. The results showed that the sequent depth decreases and energy loss and bed shear stress increases as the height, spacing of the rough bars, adverse slope and Froude number increased. In hydraulic jump on adverse slope of 1.5% and rough bed with half cylindrical roughness, sequent depth 36% decreases and the bed shear stress coefficient is 16 times of its corresponding values on smooth and horizontal bed. Some empirical relations for sequent depth ratio, relative energy loss and bed shear stress coefficient were introduced. Totally, the results obtained show that, rough bed with adverse slopes may be used to achieve better performance in stilling basins.

Keywords

• energy loss
• rough bed
• hydraulic jump
• stilling basin
• sequent depth ratio
• froude number