عنوان مقاله [English]
In the present study, the effect of vertical drop, gradually expanding and vertical screens are investigated to increase the energy dissipation efficiency of the flow. The experiments were carried out in a horizontal laboratory flume with a rectangular cross section, two vertical drop heights, and the wall expanding ratios of 0.5 to 1, the porosity ratio of the screens of 40% and 50%, and the range of Froude number of 0.86-0.92. The results showed that the use of screens and the expansion of the walls would increase energy dissipation and decrease the pool and downstream depths. The application of expanding wall, screens and the effect of simultaneous use of screens and expanding walls increases the efficiency of energy dissipation by 25, 44 and 48 percent, respectively. The porosity ratio of the screens is not much efficient in energy dissipation, but it reduces the pool depth and increases the downstream depth. Under the same hydraulic conditions, with increasing drop height, the energy dissipation rate due to the higher impact intensity of the jet passing through the drop or its downstream floor increases and the pool depth decreases. By increasing the discharge, the hydraulic jump formed in the upstream of the screens with a porosity ratio of 40% is submerged and moves upstream. However, in screens, 50% of the jump is free and moves downstream.
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