The Laboratory investigation of rotary gates to control the water level and measure the discharge in rectangular canals

In this research, a rotary gate has been used along with a rectangular-semi circular transition in order to measure and control the flow. The hydraulic efficiency of this type of transition and gate has been investigated using factors such as the level of the water level of the approaching flow and the opening angle of the gate, which is effective on the geometric location of the transition wall. The depth measurement of the flow from the upstream of the gate to its downstream was done by a depth gauge with an accuracy of 0.1 mm. The flow rate passing through the rotary gate is also estimated based on the stage-discharge curve and basic hydraulic equations, as well as three angle separation methods, data aggregation method and break point method. to check and calculate the error values in each discharge estimation method, indexes such as: average relative error index (Error), root mean square error (RMSE), standard error (SE) and normal root mean square error (NRMSE) were used. The analysis of the results obtained using the statistical indicators of the three methods mentioned above shows that all three methods have high and acceptable accuracy. In the method of using all the data and the breaking point method, the discharge is calculated by having the depth of flow at upstream, the radius and opening of the gate. Since relatively short calculations are performed in these two methods, it is sufficient for initial estimates. The results showed that the method of using each angle seems more accurate because the number of calculations in it is more. The error percentage index for the separation method is 1.30%, in the aggregated data method it is 3.29% and the breaking point method is 3.98%.Therefore, according to the results of this research, it can be seen that by using this gate and the design and construction of transition in rectangular channels, it is possible to measure the flow in irrigation and drainage networks with very good accuracy. Investigating the amount of energy loss due to the hydraulic jump of the flow after the gate shows that the amount of energy loss decreases with the increase of the opening angle.