Numerical Simulation of Flow Free Surface and Field in Circular Channel along the SideWeir in Subcritical Flow Conditions

A side weir is being installed as a flow control structure on the side of the main channel. When the water level exceeds the crest level of the side weir, the additional flow will spill over the weir crest and divert into the side channel. This type of structures has wide application in urban sewage disposal, water supply systems, drainage and flood diversion networks. In this study, the free surface of flow and the side weir discharge were simulated using FLOW-3D software. The RNG k- ε turbulence model was used for simulation of the flow field turbulence. Also the volume of fluid (VOF) scheme was applied to predict the variations of flow free surface. Comparing numerical simulations with experimental results showed the acceptable accuracy of numerical model. Next, the discharge coefficient of side weir and the free surface of flow variations were evaluated for different discharges of the main channel. Then the variation of the width of the separating stream surface from bed of the main channel toward the free surface of flow was investigated. Also, the circular channel effects on the pattern and strength of the secondary flow were studied. The effects of the main channel discharge on the stagnation point height and bed shear stress pattern were investigated. According to the subcritical flows pattern, the flow depth was increased from the side weir upstream end towards its downstream end. For all longitudinal profiles with increasing discharges within circular channel, the flow depth was increased along the side weir.