IMPROVING THE HYDRAULIC PERFORMANCE OF FAYOUMAN-TYPE WEIRS USED IN THE EGYPTIAN IRRIGATION CANALS

Gamal M. Abdel-aal, Mohamed A. Nassar, Sarah A. Helmy

Abstract


The present research aims to improve the weir characteristics by changingits geometricconfiguration. Actually, the main purpose is to solve the weir problems by allowing the passage of more water through the weir body in order to reducethe sedimentation problems in upstreamside.The combination between perforated weir and gates was experimentally studied. The experimental studies were done on wooden model of 21cm height and 2cm crest width. In addition, the study was investigated in five stages. The first stage studied the effect of changing the angle of the weir back as 90o, 60o, 30o, and 15oon the flow characteristics. In the second stage, six models of aperforated weir were studied with different slot diameters in the center point. In the third and fourth stages, the effect of varying the vertical location of the slot and its number on the flow characteristics was investigated. In the fifth stage, the perforated weir was combined by a vertical gate on its sill, the effect of combination between perforated weir and gate and changing the bevelled edge angle of the vertical gate on the flow characteristics was studied.In stage six and seven the scour was studied upstream and downstream the referenceFayoum type weir , the weir of 60 ° back angle, which contains three slots in the middle of the weir body, and the weir with three slots in the middle of the weir body combined with a gate on its sill. The studyproved that the weir of back angle = 60 °, which contains three slots in the middle of the weir body is the optimum one. It gives the optimum discharge coefficient compared to the reference Fayoum type weir,it also reduces the erosion process downstream the weir and the rates of sedimentation in the upstream side compared to the reference Fayoum type weir. Statistical model was developed for the prediction of the coefficient of discharge through the weir. Moreover, dimensional analysis was used to correlate the flow characteristics.

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