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Abstract
Water from river can be diverted either by gravity or by pumping. from the hydraulic point of view, an intake structure should be designed so as to minimize the head losses, restrict intake of sediment from the river and prevent sedimentation in the intake channel. Intake of sediment can never be completely prevented, but with the use of different techniques can be alleviated. One of the techniques is to control the diverted flow to the intake and consequently the sediment transport towards the intake.
The intake channel is likely to receive a larger proportion of the near bed flow. Once the sediment enters the intake channel, the near bed component of the secondary circulation sweeps into where it accumulates. These problems are a result of the flow patterns induced by sudden change in flow direction that gives rise to a coherent but complex three dimensional flow structure that characterized by strong secondary circulation.
the magnitude and the direction of the sediment transport toward the diversion channel, depends on the radius of curvature of the diverted flow. Decreasing the radius of curvature results in diverting more sediment into the intake channel and increasing of the secondary currents at the entrance of the intake channel. This leads to the increase of the scour zone beside the outer wall of the intake channel and the separation zone, (deposition zone), beside the inner wall
Enhancing the velocity distribution at the intake channel results in increasing the radius of curvature of the diverted flow consequently, reducing of the area over which separation zone occurs and the amount of sediment that enters the intake channel.
he angle of diversion of the diverted flow is an important factor. it enhances the velocity distribution at the intake channel, but it is not easy to be determined analytically. Thus this study was initiated in order to contribute in determining the optimum angle of diversion experimentally.
In this study, two experimental formulae, (depending on the most effective parameters on the mentioned phenomena), were developed to help in the intake channels hydraulic design, such that the water with its sediment will be transported with a minimum sediment deposition in the intake channel.
The results of the developed formulae were satisfactory in the predictions of sedimentation problems at two locations at the Nile River, Upper Egypt. The first location was at Beni-Hemil Pump Station, in which the diversion angle of the intake channel was 104o. The second location was at El-Walydia Power Plant, in which the diversion angle of the intake channel was 90°.