3D Simulation of Supercritical Flow Characteristics in Circular Channels with Side Weirs

The circular channels with side weirs are widely used to regulate the flow and control the water depth in the urban sewage disposal systems. In this study, the turbulence of flow field and variation of the free surface of supercritical flow in a circular channel with a side weir are simulated using FLOW-3D software, the RNG k-ε turbulence model and VOF scheme. Comparison between the numerical simulation and laboratory measurements shows that the numerical model has simulated the free surface and flow field profile with reasonable accuracy. According to the numerical simulation, the flow depth is decreased along the side weir. In all simulations, a free surface drop has happened at the upstream beginning of the side weir. There is also a surface jump at the downstream end of the side weir. The change of specific energy along the side weir for the supercritical flow regime is almost constant and the energy loss is not significant but by increasing the side weir length the energy difference between the upstream and downstream of the side weir increases. The velocity field analysis indicates that the maximum longitudinal and lateral flow velocities happen at the end and middle of the side weir, respectively. Also in each cross-section, the maximum vertical velocity happens in vicinity of the side weir.