Study coefficient of discharge for a combined free flow over weir and under gate for multi cases

الملخص EN

Weirs and gates are the common and important structures which are used in controlling and adjusting the flow in irrigation channel.

One disadvantage of the gates is the possibilities of retaining the floating materials which can be resolved if they combined with the weirs.

Also sedimentation problem in weir can be resolved by combination of weirs with sluice gates.

These combined structures have a new hydraulic condition that is different with weir condition solely or we have only gate.

This study was done in the fluid lab of civil engineering in Babylon University.

This research presents the results of an experimental study on the hydraulic characteristics of weirs and combined weirs under multi cases, these cases were (rectangle weir, v-notch weir, semicircular weir, rectangular combined weir with a rectangular gate, v-notch combined weir with a rectangular gate, semi-circular combined weir with a rectangular gate, and semicircular combined weir with a semi-circular gate).

The results showed that the experiments erected on the notches were obtained for discharge coefficient Cd as follows : Rectangular weir Cd = 0.607, V_ notch Cd = 0.630, Semicircular weir Cd = 0.693, Combined V-notch weir and Rectangular gate Cd = 0.779, Combined Rectangular weir and Rectangular gate Cd = 0.751, Combined semicircular weir and Rectangular gate Cd = 0.781 and Combined semicircular weir and semicircular gate Cd = 0.797.

We found the values Cd in the Compound semicircular weir and semicircular gate are the best in terms of being a once hydraulic values Cd higher than the other notches.