The discharge consists of both weir flow and orifice flow after opening a flap gate,which brings difficulty to hydraulic engineering design.The previous research was mainly aimed at determining the comprehensive discharge coefficient.To discuss the mutual influence of the weir flow and the orifice flow when they function separately,the physical model experiments were conducted to investigate the influence of the flow and the level of the tail water onto the flow passage ability through the flap gate,under the condition of the maximum opening of the gate.The tests involved the combinations of the flow rates of 0.06,0.08,0.10,and 0.12 m3/s and the levels of the tail water of 0.50,0.55,0.60 and 0.65 m,a total of sixteen testing conditions.The results showed that when the level of tail water was constant,the discharge coefficient and flow rate were positively correlated;when the flow rate was constant,the discharge coefficient and the level of downstream water were negatively correlated.While these findings were based on the maximum opening of the flap gate in this study,more experiments will be carried out to study the discharge coefficients under other conditions.
