عنوان مقاله [English]
Background and objectives: weirs are widely used to measure flow, water deviation and flow control in open channels. So far, most of the weirs used in the diversion dams were linear. In this study, the effect of sediment properties transmitted in the main channel and intake channel has been studied by changing the magnification of the weir.
Materials and Methods: The research was carried out at the Hydraulic Laboratory of the Water Engineering Department of Bu-Ali Sina University. The experiments were carried out in flume lengths of 10 meters, width of 83 cm and height of 50 cm. weirs, gate and intake channels with accessories and reservoir of sediment collection were also designed and added to the collection. For testing, non-adherent sediment particles with a grain size of approximately the same size and with a diameter of 0.35 mm were used. Experiments were carried out with a layer of sediments of thickness of 4 cm and slope of 0.002 and in two discharges of 40 and 60 liters per second. At first, intake gate and sluice way was closed and a flow with a small discharge entranced until the flow passed on the weir. Then the discharge increased to 60 or 40 liters per second. Then the intake gate was opened to a certain amount and the experiments were carried out for a certain period of time. Then, the entered sediments into the intake channel and also the accumulated sediment in the mesh of the end of main channel were collected, dried and weighted, and the concentration of sediments entering the intake channel and also downstream of sluice way were calculated.
Results: The results showed that, in equivalent intake discharge ratio, with increasing discharge from 40 liters to 60 liters, the concentration of sediments in the intake channel increases. Also in equivalent intake discharge ratio, increasing the weir magnification increases the concentration in the intake channel. Also the increase in intake discharge ratio and the increase of the sluice gate discharge ratio, increase the concentration of sediments in the intake channel. The same applies to the sluice gate. This means that increasing the magnification, increasing discharge, intake discharge ratio and sluice gate discharge ratio will increase the concentration of sediment input to the intake channel.
Conclusion: Increasing the magnification reduces the flow head and also reduces the flow depth in the upstream, and as a result, the shear stress rate of the flow increases, which results in the transfer of more sediment to the downstream and, consequently, to the intake channel. Increasing the opening of the intake gate and, consequently, increasing the intake discharge rate, also increases the concentration of sediments deposited to the intake channel, However, increasing the weir magnitude and also increasing the sluice gate discharge ratio has no Significant influence on the sediment concentration ratio of the canal intake to the main channel.