Effect of Radial Arrangement of Submerged Vanes in Increasing the Flushing Efficiency of Dam Reservoir

Pressurized flushing is one of the common methods in hydraulic flushing of dam reservoirs. In this method, sediments settled in the reservoir are released out together with water flow using the bottom outlet of the dam. In this research, by employing the submerged vanes with radial arrangementin front of the bottom outlet, effect of this arrangement in enhancement of the vortex flow and pressurized flushing efficiency were investigated. The effect of different parameters of radial arrangement including cross distance of the main vanes (Lm), distance between the main and side vanes (Ls) and the distance of vanes from the side wall (Lv) on this phenomenon were investigated in three different water depths of the reservoir (20, 30 and 40 cm). Based on the results, the optimal non-dimensional lengths values of the radial arrangement parameters were obtained as Lm/D=0.5, Ls/D= 0.25 and Lv/D=0.2 (D, diameter of bottom outlet). In the best radial arrangement parameters of the vanes in the different hydraulic condition, flushing efficiency increased about 11.33 times compared to the control model. In radial arrangement, with increasing the water depth of reservoir, the flushing performance increased. This condition, more flushing in high water depth, is a comparative advantage for flushing. In other words, the flushing operation has more efficiency in the full condition of the reservoir and it is not necessary to empty the reservoir.