Investigating the process of changing the discharge coefficient of the flow passing through the combined structure of rectangular sharp-crested weir with multiple-gates

To investigate the effect of the number and dimensions of the gates-weir structure, 117 experimental tests were carried out at different flow rates, numbers and dimensions of square gates. The experiments were carried out in a laboratory flume with a length of 12 m. The results showed that with the increase in the number and dimensions of the gates in combined weir-gate structure, the combined discharge coefficient was increased. These changes are such that the combined discharge coefficient is increased by 3.8% with the increase of each gate. The results showed that the lowest and the highest increase in the flow coefficient was observed in the comparison between the single gate and the 5-gate condition compared to the no-gate condition by 16% and 18%, respectively. In the following, a relationship was presented to determine the combined discharge coefficient with RMSE = 0.001.