Use of Side Slots and Submerged Vanes for Sediment Flushing in Upstream of Duckbill Weirs

Duckbill weir is one of the water level control structures in irrigation networks which has been attracted by many engineers. Since sediments are transported in irrigation networks, they are accumulated at upstream of the duckbill weirs and cause some operational problems. In this study, side slots and submerged vanes were used in addition of frontal slot to prevent sediment accumulation in upstream of weir. The experiments were conducted in a rectangular flume with 12 m length and 0.6 m width. The vanes had different heights and were arranged in two column with four rows which were perpendicular to side wall direction. The results showed that the submerged vanes induced the secondary flow which was so effective for sediment flushing through the side slots especially for higher value of  (H was head over side wall and p was the height of weir). Submerged vanes having the identical heights of the weir not only increased the sediment flushing to downstream, but also increased the discharge ratio up to 7 percent. The results showed that duckbill weir efficiency (which was defined as the ratio of sediment trap to flow capacity of weir minus one) was increased to 65 percent by use of the submerged vanes indicating that the maximum flushing and flow conveyance were occurred in a given upstream head. For preventing the sediment accumulation in upstream of the duckbill weir, use the side slots together with submerged vanes for a values of H/p= 0.1-0.5 is proposed.