Experimental study on turbulent characteristics of open channel flow at 30° diversion angle

The main and branch channels are positioned vertically in irrigated areas, and damage occurs at the side wall structure near the bleeder, owing to scouring and deposition of sediment particles. The divergence and confluence angles of natural rivers typically acute. In this paper, the open channel at a 30° water separation angle was used as the research object. The three-dimensional instantaneous velocity was measured using an acoustic Doppler velocimeter, and the distribution of the average velocity, circulation intensity, turbulence intensity, turbulence kinetic energy and bed shear stress at typical cross-sections were analyzed. The experimental results showed that for the 30° water separation angle, the lateral velocity of the water flow at the water outlet varied significantly along the canal width, and easily formed circulations, causing local erosion and deposition. The turbulent intensity near the branch channel changed sharply and irregularly, and the maximum value was observed at the forefront section of the bleeder. The kinetic energy of the lower flow significantly exceeded that of the upper flow at the water outlet, and the higher value was mostly concentrated near the water inlet of the side channel. The bed shear stress at the end of the water diversion section of the main channel was high, eroding the side wall and reducing stability. Compared to the right bleeder, the 30° water separation angle adversely caused the sediment particles to enter the side channel and decreased the erosion rate of the water flow to the bottom and side walls of the channel. This study provides a reference for channel design and operation in irrigation areas.