Numerical simulation of velocity distribution and pollution transport in a two-stage channel with vegetation on a floodplain

Abstract

Compound cross-sections are common forms of river cross-sections in nature. Due to their more complex structure, it is more difficult to study their hydrodynamic and pollutant transport characteristics. How to establish effective models to simulate such conditions has recently become a hot topic of attention. The work presented in this article establishes a numerical model to simulate the flow velocity and pollutant transport in a compound cross-section channel using the lattice Boltzmann method and random displacement method to study the hydrodynamic and pollutant transport characteristics under flexible vegetation cover. The model can effectively generalize the vegetation drag force on the floodplain of the compound cross-section and provide the distribution pattern of flow velocity under uneven vegetation cover. At the same time, the lateral diffusion coefficients of pollutants on the main channel and floodplain are provided separately. These have higher accuracy than those determined by traditional methods that rely on simple longitudinal diffusion coefficients. This study can provide a theoretical reference for optimizing vegetation planting in compound cross-section channels.