A Large-Eddy Simulation Study of Dispersion of Particles Released within a Plant Canopy

The interaction between vegetation and the atmospheric boundary layer results in complex turbulence structures and high turbulence intensities, driving the release and transport of biological particles such as seeds, pollens, and pathogenic spores. Particles that have escaped the canopy region into the free flow above are likely to travel farther from the release location. A large-eddy simulation model is used to study the effects of turbulence, canopy, and particle properties as well as release height on the probability of particles escaping from the canopy region. The canopy is represented as a horizontally homogeneous aerodynamic drag field in the resolved momentum equation. Simulation results of mean flow and turbulence statistics are in good agreement with previous studies and field experimental data obtained in a large commercial corn field. Particles represented as a continuous Eulerian concentration field are released at a constant rate inside the canopy. Advection by resolved scales and gravitational settling are explicitly represented, while dispersion by subgrid-scales and deposition on canopy elements are parameterized. Mean particle concentrations are compared to field experimental data of artificial point source releases. Sensitivity studies are performed to investigate the effects of particle properties and release height on the probability of particles escaping from the canopy and the consequences for downwind dispersion.