Application of Computational Fluid Dynamics in Investigating Orifice Spillway Flow

Orifice spillways are provided in run-of-the river diversion dams in Himalaya’s region where management of sediment along with flood is the main issue. Analysis of hydraulic behavior of flow over orifice spillway is very significant considering safety and efficiency of dam. Orifice spillway are susceptible to cavitation, scouring, downstream erosion and high velocity. Conventionally, such complex hydraulics problems are encountered by physical modelling which is time consuming and uneconomical. However, computational fluid dynamics modelling is advantageous because of high performance computing. Performance and reliability of numerical modelling depend upon grid selection or grid convergence studies. Paper aims at selection of grid for orifice spillway with ski-jump dissipater, discharging capacity of spillway, pressure distribution over the spillway, air entrainment effect, comparisons of turbulence model by using Flow 3D based upon volume of fluid technique. Further, the numerical model results were validated against results obtained on a physical model of 1:40 scale and the model fit were estimated using statistical parameters R2 and RMSE. Overall, considerable accuracy of CFD as a preliminary and supplementary tool for orifice spillway analysis was seen.