Numerical Simulation of Confluence Flow in a Degraded Bed Under Different Turbulence Models with a Comparison of Rigid Lid and Volume of Fluid

Abstract

Abstract The fluid dynamics of open channel confluences are highly complex due to the flow separation, mixing and secondary currents. Although numerous studies in the past few decades have focused on the numerical simulation of confluence flow, deformed beds were rarely used. This study attempts to address this issue through numerical simulation of the flow behavior in an open channel confluence flume with an equilibrium degraded bed in OpenFOAM. In the present study, six turbulence models, including Reynolds-Averaged Navier-Stokes (RANS) (standard k–ε, realizable k–ε, k–ω SST, V2-f), large-eddy simulation (LES) and detached eddy simulation (DES) models were performed using rigid lid and volume of fluid (VoF) methods. The accuracy of the models was statistically analyzed by comparing with the observation data, and their performance was prioritized accordingly. The results of this study demonstrated that the LES model had the best performance, with a minimum average normalized mean square error (NRMSE) of 9% under the VoF assumption and 27% under the rigid lid method.