Flow simulation of turbulent and mean advective velocity and scalar fields across a canopy edge

The structure of turblence in flows blowing from an open field to a plant canopy wass investigated above and below canopy using the third-order closure model. The computation results of the steady-state model provide fields of velocity, pressure, Reynolds stress, TKE, and third-order moments in the domain. The model was run for three different canopies, of which leaf area indices are LAI=0.2, 0.8, and 3.

Traditional turbulent parameters used in lower order closure methods, such as the zero plane displacement and roughness length were also calculated. These showed that for the cnaopy, the zero plane displacement normalized by canopy height rose monotonically with increasing LAI, while the roughness length was maximum at intermediate LAI. Mean windshear and the Reynolds stress also reached a maximum at approximately the same LAI.

The horizontal and vertical turbulent transport of a passive scalar was compared to mean horizontal and vertical convergence/divergence transport. This was compared to previously published work where we showed a simple dimensionless number could be used to quantify the magnitude of mean transport compared to vertical turbulent transport.