Local Scour Around Lateral Intakes in 180 Degree Curved Channel

Abstract

Local scour on hydraulic structures is one of the most significant problems which are always considered by hydraulic engineers. If the local scour depth is estimated less than real one it can lead the hydraulic structure to fail. On the other hand, if this depth is estimated more than real local scour depth, that construction has no economical justification. Lateral intake is one the hydraulic structures which are used for water conveyance for the purpose of domestic, agricultural and industrial use. Since streamlines near the lateral intake are curved and diverted to lateral intake, some vortices are formed and local scour is observed near the lateral intake. Due to the secondary flow in a river bend, the scour develops near the outer bank and sediment moves toward the inner bank from the outer bank of the bend. Therefore the outer bank of the bend is best location for lateral intake. In this study, experiments were conducted on 180 degree curved channel. In order to consider the effect of lateral intake position on the maximum local scour depth, the lateral intake was situated on 90, 115 and 150 degree. The experiments showed that two scour holes, one in the upstream and the other in the downstream edge of lateral intake, are formed near the lateral intake. Moreover it was found that the maximum depth of scour hole occurs on 90° location. Also the length of scour hole in 150° is the longest.