Influence of setting angle for guide bar on velocity characteristics of spiral flow in cross-sections between piped carriages

This study aims to explore the velocity characteristics of spiral flow between piped carriages under various setting angles of the guide bar. A combined theoretical and simulation test was adopted, where the main control variable was set as the setting angle of the guide bar. The results showed that there was basically the same trend in the distribution of axial velocity at the section of two carriages in pipeline car under the different setting angles of the guide bar, where both spread inward from the pipe wall and then outward from the pipe axis. There was an overall large value of the axial velocity at each section of car carriages, with a maximum of up to 3 m/s. In the rear car, there was a positive or negative velocity of axial flow at the cross section, indicating the backflow occurred. The velocity values of water flow were basically positive at the section of the pipeline in the middle and front of the car. There was a gradual distribution of 120° rotation symmetry in both circumferential velocity and radial flow velocity at cross-sections between piped carriages with the increase in the installation angle of the guide bar. The value of circumferential velocity was larger, but that of radial velocity was smaller in the directions of 0°, 120°, and 240° polar axes. The intensity of circumferential velocity was much stronger as the setting angle of the guide bar increased, where the maximum circumferential velocity reached 1.5 m/s, indicating a great influence of setting angle on the circumferential velocity. Furthermore, the circumferential flow velocity was positive or negative, indicating two directions, including counterclockwise and clockwise. In percentage columnar accumulation, there was a stepladder characteristic of circumferential flow velocity under different setting angles of the guide bar. A positive correlation was found between the circumferential flow velocity and the setting angle of the guide bar. The radial velocity basically fluctuated between -1-1 m/s, where there was a relatively large area with zero. The radial flow velocity was also much smaller, compared with the axial and circumferential flow velocity. Two directions were found in the positive or negative radial flow velocity: inward and outward the circle center along the diameter. The finding can provide theoretical support for the spiral flow of pipelines and the popularization of piped hydraulic transportation. © 2021, Editorial Department of the Transactions of the Chinese Society of Agricultural Engineering. All right reserved.