Laboratory study of the interaction of convection and congressional overflow in underpasses on the flow rate of overflow in open and submerged states

Subject Areas : hydraulic structures

roozbeh riazi ¹ (Assistant Prof. of Department of Civil Engineering, Dehdasht Branch, Islamic Azad University, Dehdasht, Iran.)
Maryam khanbab ² (M.s Student, Department of Water Science Engineering, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran)

Received: 2022-04-25 Accepted : 2022-05-17 Published : 2022-05-22

Keywords: discharge coefficient, culvert, modular limit, labyrinth weir,

Abstract :

Weirs are hydraulic structures used to control the water level in canals and rivers, and when the water reaches the height of the weirs, they start working and draw water out of the system. This laboratory study analyzes hydraulic changes on four types of congressional series with different lengths (L / P) in free and submerged flow modes. Also, the effect of Calvert placement downstream of the overflow at three distances (d / p = 0.2,0.4,0.6) on the upstream and downstream flow characteristics were investigated, and the results showed that in all four types of the congressional weir, with increasing The hydraulic load ratio increases to about h_0 / P = 0.1 of the flow rate and in this ratio reaches its value and then decreases after this value. Also, the immersion threshold increases with increasing overflow length (L / P). (t / h) ^ * also increases. Relatively longer overflow in the congressional mode than the sharp-edged overflow improves the coefficient of run and, on the other hand, increases the immersion threshold. The results showed that the Calvert at a distance closer to the overflow could affect the characteristics of the flow after the overflow due to the formation of the first wave passing through the overflow (Xw) and increased the flow after the overflow in the submerged state and increased. Immersion threshold and increase immersion ratio (t / h). Moreover,