Document Type : Research Article
Civil Engineering Faculty, University of Tabriz, Tabriz, Iran
Professor, Faculty of Civil Engineering, University of Tabriz, Tabriz, Iran
Associate Professor, Department of Civil Engineering, Faculty of Engineering, University of Maragheh, Maragheh, Iran.
In the present study, the effect of vertical drop, gradually expanding and vertical screens are investigated to increase the efficiency of the energy dissipation 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 expansion of the walls would increase energy dissipation and decrease the pool depth and the downstream depth. The application of expanding wall, screen 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 screen is not much efficient in energy dissipation, but it reduces the pool depth and increases the downstream depth. In the same hydraulic conditions, energy dissipation is increased and the depth of the pool decreases by increasing the height of the drops due to the increased jet severity over the drop striking the downstream bed. By increasing the discharge, the hydraulic jump formed in the upstream of the screens with a porosity ratio of 40% is submerged and moves upwards. However, in screens 50% of the jump is free and moves downward.