Numerical modelling for design of spillway refurbishing

Mathematical modelling of single spillways is well documented in literature. For parallel spillways however, there is a lack of documented, verified, and validated cases. Here, in this article, ANSYS-CFX is used to simulate the flow over three parallel ogee-crested spillways. For mesh size verification, a grid convergence study is performed by Richardson extrapolation. The turbulence model chosen for this simulation is the k-e model and the volume of fluid method is used to simulate the water-air interface. This article details the models ability to accurately predict flow distribution at the spillways, and the water levels. The mesh is kept relatively coarse at the channel inlet with increased mesh density at the spillways. The results are validated against experimental data from Vattenfall AB, R&Ds laboratories. The geometry and boundary conditions of the experiment are tailored for CFD. The flow rate of each spillway is measured separately with high accuracy, and for several different inlet volumetric flows. The simulation results lie within the error estimates of the measuring tools used in the experiments, within ±1%. The volume flow rate differences between the three outlets is very small, within ±1%.