摘要：Weir and gates are widely used in controlling and measuring flow in irrigation projects due to simple and relatively accurate relations. The weir- gate combination model, with the ability to simultaneously transfer sediment material from the bottom of the gate and suspended material from the weir, prevents the accumulation of sediment and suspended material behind the weir system, and helps to increase the measurement accuracy and passing of flow. In the present study, the effect of plan shape change (square, triangular, and trapezoidal) and gate height on the coefficient of labyrinth weir-gate combination model was investigated in a laboratory study. And all experiments were carried out with five different discharges (5, 10, 15, 20 and 25 L/S), and a total of 270 tests. All of the square, triangular and trapezoidal models, such as (simple labyrinth weir, simple labyrinth weir-with gate, labyrinth weir, labyrinth weir-with gate) with 5 different discharges, labyrinth with 2 different angles and gates with two different types were considered and the results showed that the coefficient in the combined model of trapezoidal labyrinth weir-gate was more than the combined model of labyrinth weir-triangular gate as well as the coefficient in the combined model of labyrinth weir-triangular gate is more than the labyrinth weir-square gate. In fact, the effect of the plan shape change of weir from square to triangular and trapezoidal models is respectively, in direction of increasing the coefficient. Finally, from square, triangular and trapezoidal labyrinth weirs, the overall results from SPSS software show that the highest flow can be obtained using the labyrinth weir- trapezoidal gate structure.
