A fast-response model of turbulence and passive scalar transport in row-organized canopies

For simulation -intensive studies of aerial crop disease transport such as source term estimation, fast and accurate physics models are required. In crops planted in rows with sparse aisles like vineyards and other trellised crops (so-called "row -organized canopies"or ROCs), the impact of the vegetation structure on the flow limits the validity of the simplest models (i.e., Gaussian plumes). The present work introduces a model for the Reynolds stresses near an ROC, which is implemented in QES (Quick Environmental Simulation), a suite of fast -response modeling tools that includes a GPU-accelerated mass -consistent 3D wind solver, an eddy viscosity -based turbulence module, and a Lagrangian dispersion model. Additionally, a novel leaf deposition model based on improved turbulent flow parameterizations is implemented and evaluated. The ROC turbulence model is evaluated against sonic anemometer data from a vineyard. The overall QES-ROC dispersion model is then compared against a series of particle release experiments performed in the same vineyard. The new turbulence model captures the shape and general behavior of the shear stresses as the forcing wind direction changes, and accurately represents anisotropy in the normal stresses. Both traditional paired -in -space metrics and more detailed measures of 3D plume shape are used in the plume comparison. Modeled plumes spread wider in row -perpendicular winds than in row -parallel winds, as is seen in the experimental plumes, and veer appropriately in the direction of the row during row -diagonal winds due to mean wind channeling. Vertical spread in the QES model appears to be insufficient, and possible explanations are explored.