Abstract:

The influence of the water inlet on the flow pattern in front of the gate and the variation law of the flow coefficient and head loss of the trapezoidal control gate under different slopes and water diversion angles are studied. The flow formula of the trapezoidal control gate is established, and the head loss law of the trapezoidal control gate is explored, which provides support for the accuracy of water measurement and control in the irrigation area. A total of 495 groups of tests with different opening degrees and different water heads were set up in three slopes ( m = 1.5,1.75 and 2 ) and five water diversion angles ( θ = 30 °, 45 °, 60 °, 75 ° and 90 ° ). The over-current test of the trapezoidal control gate under different water diversion conditions was carried out. The flow pattern of the water outlet was observed and the causes were analyzed. The flow formula of the trapezoidal control gate was established by dimensional analysis method, and the relative head loss of the control gate was calculated. The backwater area is formed in front of the control gate. The correlation coefficient of the flow calculation formula of the control gate is R² = 0.934, and the average relative error of the flow is 2.83 %. The relative head loss decreases with the increase of the relative opening of the control gate. The flow formula of the trapezoidal control gate has high accuracy, which can provide a basis for the flow measurement of the trapezoidal channel in the irrigation area.

Key words: trapezoidal gate, control gate, water inlet, head loss, flow coefficient, flow formula