Numerical modeling of pollution transport in flexible vegetation

Abstract

• Large eddy simulation model of pollution transport with flexible vegetation. • Model proposed for recognizing flexible vegetation. • Subgrid length scale model modified into a mixed-scale model. • Random walk model used to describe the mechanical dispersion . • Recognizing flexible vegetation increases the vertical mixing of pollution. In this study, we present a large eddy simulation model of the flow and scalar transport in an open channel with flexible vegetation. We propose a model for recognizing flexible vegetation to simulate the deflected height of vegetation with flexibility. A mixed scale model is modified for canopy turbulence modeling. A random walk model is used to calculate the mechanical dispersion during the scalar transport process within the canopy. A two-stage second-order nonlinear strong stability-preserving Runge–Kutta scheme is combined with the operator splitting algorithm to solve the governing equations. We verified the numerical model based on previously reported experimental data and the comparisons between the simulations and measurements were favorable. The model was then applied to simulate scalar transport within flexible vegetation, where the simulations showed that the recognition of flexible vegetation could enhance the vertical mixing and diffusion of the scalar concentration.