Hydraulic Design of A Multi-Level Intake Structure

Abstract

In the present work design of a multi level intake is explained for a 65m high rock fill dam. This multi-level intake structure was designed for irrigation purposes with a design discharge of 20 m3/s. This structure, standing vertically in the reservoir, was 65m high and had a rectangular cross section which its dimensions were different at different elevations. Four intakes were considered in different elevations in this structure. All intakes were located at one side of the intake structure, each controlled by an independent slide gate. To be able to operate these gates in 4 different gate slots, each intake was recessed in comparison with the intake located at the lower elevation. A separate slot was also used for the trash rack. As a part of the design process, a 1:20 scale model was constructed. This hydraulic model study was conducted to collect hydraulic design data for the proposed intake structure and to ensure satisfactory hydraulic performance. The scale model was tested to determine head losses, discharge capacity and the potential vortex formation which could affect the performance of the structure and mechanical equipment. The hydraulic model showed that flow condition along the tower and at intakes is satisfactory. No separation at transitions and especially at 90o curvature of the flow from the intakes to the tower structure was observed. In addition pressures measured at different points were in acceptable range. A minimum water level was also found for each intake through experiment at which vortex did not form in the reservoir.