Numerical Investigation of Flow and Pollutant Dispersion in Various Meandering Channels

The meandering of natural rivers generates very complicated flow structure including turbulent and highly three dimensional phenomena. The advection effect, which is caused by secondary and turbulent flow, severely influences on the pollutant mixing in natural rivers. Therefore, understanding the mechanism of flow structures and mixing process in meandering channels are needed. In this study, three-dimensional numerical investigation of the flow pattern and pollutant dispersion in various meandering channels is carried out by a specific solver, which is developed and coupled into an open source CFD package, the OpenFOAM. In the standard library of OpenFOAM, the numerical solution is designated only for a passive scalar transport, and it can deal only for a given stationary velocity field and constant diffusion coefficient, so that it cannot take in account the effect of turbulent flows. In the new solver, the scalar transport equation is solved in combination with RANS (Reynolds Averaged Navier-Stokes) and LES (Large Eddy Simulation) models.

The new solver has been validated against typical benchmarking experiments, such as Rosovskii’s De Vriend’s, Tamai’s and Chang’s experiments. The comparisons between the simulations and observations show very good agreements on the flow patterns and pollutant dispersions.