Performances of Different Turbulence Models in Predicting Important Characteristics of Steady Flow in Combined Open Channel Junction

Combining open channel junction (COCJ) hydraulics is characterized by three-dimensional (3D) flow field, including flow separation zone (FSZ) and shear layers which are enriched with strong vorticities and high turbulence. The present study investigates the performance of five different eddy-viscosity turbulence models (Spalart-Allmaras, Standard k-e, Realizable k-e, Renormalized k-e; and Shear Stress Transport k-w with curvature correction), Reynolds Stress Model (RSM), and Detached Eddy Simulation (DES) to predict the characteristic features in COCJ. The 3D flow field is simulated using computational fluid dynamics (CFD) software Ansys Fluent, version 17.2. Experimental results available in the literature are used as the reference case for model validation. Present simulated results show that the longitudinal velocity field is predicted reasonably well by all the models, except in the region associated with the FSZ. DES model shows an improvement in simulating the flow field associated with the FSZ. Simulated results demonstrate that the transient Reynolds-Averaged Navier-Stokes (RANS) models could not capture the instantaneous flow features of the shear layer. The instantaneous vortices and the Kelvin-Helmholtz breakdown of the sheet-shaped turbulent structures within the shear layer associated with the FSZ could not be predicted by the RANS model.