Experimental Study of the Effect of Suppressed and Non-suppressed Sill on Sluice Gate Discharge Coefficient under Free-Flow Condition

Vertical sluice gate is a structure that is installed on the channel to control the upstream flow. The purpose of this study is to investigate the effect of sluice gate opening and effect of the presence of suppressed and non-suppressed sill below sluice gate on the discharge coefficient under free-flow conditions. Therefore, rectangular sills with different widths of 2.5, 5, 7.5, 10, 15, 20, 25 and 30cm at constant gate opening and sluice gate with openings of 1, 2 and 4cm in without sill state were studied. The results showed that in the without sill state, the amount of gate opening is inversely related to the discharge coefficient, so that by decreasing the gate opening rate, the discharge coefficient increases. On average, the discharge coefficient of 1cm gate opening is higher than that of 2 and 4cm, 7.75% and 16.51%, respectively. The results also showed that with increasing the sill width and thus reducing the total area of the flow through the gate, the discharge coefficient increases and vice versa. The presence of a sill with a minimum width compared to the non-sill state in a specified opening leads to an increase in the discharge coefficient. At the same opening in the without sill state and suppressed sill at a constant flow, the sluice gate discharge coefficient with sill increases in comparison with no sill state. In the present study, based on the dimensionless parameters, nonlinear regression polynomial relations were presented by combining all experimental data to predict the discharge coefficient in without and with sill state in different widths.