Studying the channel confluence hydraulics using Eddy viscosity models and Reynolds stress model

Abstract

Flow features at a 90-degree equal-width open-channel confluence are studied by using Computational Fluid Dynamics (CFD) software Fluent (version 17.2). Three-dimensional Reynolds-averaged Navier–Stokes (RANS) equations supplemented with several turbulence models are solved numerically. The volume of fluid (VOF) method is used to track the water surface elevation (WSE). Three eddy viscosity turbulence models, i.e. Spalart–Allmras, Standard k-∈, SST k-ω and the Reynolds Stress Model (RSM) are chosen to model the turbulence. Simulated velocity fields and WSE match satisfactorily with the corresponding experimental results available in the literature. However, RSM shows more deviation in predicting the velocity field towards the left bank of the channel. Standard k-∈ model under-predicts the maximum width and length of the separation zone. Spalart–Allmras and SST k-ω models simulate the maximum width of the separation zone more accurately. However, these two models highly over-predict the L∗s. RSM model over-predicts the maximum width and length of the separation zone. Simulated WSE is more accurate using standard k-∈ model than the other turbulence models.