Effect of Semi-Cylinder Structure Position on Pressurized Flushing Efficiency of Reservoirs

This study is done with the purpose of developing an effective method to release sediment out of dam reservoirs. Semi-cylinder is employed in front of bottom outlet to enhance vortex flow and their effects were tested. On the semi-cylinder، gaps with different height and length were created in such a way that the top of the gap was in the bed level and as well as the bottom level of the outlet. The experiments were carried out on the semi-cylinder with different diameters and water levels. The results indicated that for a given water level flushing capacity was less sensitive to gap length. When the ratio of semi-cylinder diameter to length of gaps equals to 2، the maximum flushing capacity occurred. The flushing capacity variation with respected to the gap height is large، and when the ratio of gap height to diameter of the semi-cylinder was 0. 6 flushing capacity increased significantly. Furthermore when diameter of semi-cylinder was 2. 5 times larger than the bottom outlet diameter the maximum amount of flushing capacity was occurred. This flushing capacity was 30 times more than the rate in which no semi-cylinder was installed.