Numerical investigation of Flow over Rectangular Side weir in a Circular Channel

Side weir is one of most important structures in drainage system, irrigation, flood protection, and urban sewage systems. Therefore, the hydraulic behavior of side weirs received a level of interest by many researchers. The water surface profiles over rectangular side weirs in circular channel were investigated experimentally by many researchers in past. In present study, hydraulic behavior of a side weir is simulated by FLOW-3D software. RNG model for turbulence simulation and VOF model for water surface simulation were applied. At first, the water surface profiles and the discharges performances from CFD analyses were validated with the experimental results. The results show good agreements between CFD and experimental results in the subcritical regime. Then free surface flow and flow pattern over a side weir is simulated and effects of upstream Froude number on them are investigated. Various turbulence models were tested to determine the sensitivity of the free surface over a rectangular side weir. The results showed, RNG k- ε turbulence model can be used to predict the various characteristics of the side weir flow and give close results compared to other turbulence models.