Feasibility of Reducing the Surface of Submerged Vanes by Maintaining Efficiency in the River Bend

The outer bend of the river bank is one of the most suitable locations for water diversion intakes. During floods, sediments enter the lateral intakes with the diversion flow, causing such problems as sediment accumulation at the entrance, canal and downstream of the intake, reducing the water intake capacity from the river. An efficient and effective method in reducing the inflow of sediment is using submerged vanes. In the present study a laboratory flume with 180-degree bend was used. This bend behaves similar to most bends of the meandering rivers, such as Karun River in order to physically model the possibility of reducing the area and the scour hole of the submerged vanes, while maintaining their efficiency. The vanes consisted of four different shapes, including a simple rectangle, and three other rectangular shapes modified with 30, 45, and 60 degree cuts in their front edge. They were placed separately and in a two-row arrangement, at a 110 degree angle, in front of the water intake opening, which were connected to the main canal in a 45 degree angle; and were examined and evaluated under similar hydraulic conditions. The findings of this study show that with an increase in the cut angle in the front edge of the submerged vanes (θ), there is a decrease in the size of the scour hole around them. Fixed in a 30 degree angle, for 60 degrees θ vanes, and for relative diversion discharge with a unit width of up to 0.25, the efficiency and performance of submerged vanes were maintained despite an approximately 29% reduction in their areas. Moreover, the depth of scour holes around them were reduced approximately by 29.4%, compared to simple rectangular vanes.