Numerical Simulation of Flow over Rectangular Broad-crested Weir with Upstream and Downstream Side Slopes Using Fluent Model

Weir is one of the oldest human-made hydraulic structures that is used for measurement and regulation of the flow. The flow over weir is turbulent، with water and air being mixed together. In this study two-dimensional model of water flow over two kinds of broad-crested weirs including ARB and BRA with upstream and downstream side slopes has been simulated. The FLUENT computational fluid dynamic codes which uses standard k−ε model was employed to compute the free surface of water using the VOF model. The results for hydraulic parameters of discharge coefficient، velocity and boundary layer development were compared with those obtained from the experimental results and previous equations. The results showed that the standard k−ε turbulence and VOF models were suitable to predict water surface profile over broad-crested weirs and to determine the discharge coefficient and velocity profiles at different distances over the weir،s crest. The maximum relative error of the predicted hydraulic head and discharge coefficient were acceptable with the values of 4. 06 and 6. 54 % respectively.