Plume dispersion simulation in low wind conditions in stable and convective boundary layers

The present study proposes a steady-state mathematical model for dispersion of contaminants in low winds that takes into account the along-wind diffusion. The solution of the advection–diffusion equation for these conditions is obtained applying the Laplace transform, considering the planetary boundary layer as a multilayer system. The eddy diffusivities used in the K-diffusion model were derived from the local similarity and Taylorʹs diffusion theory. The eddy diffusivities are functions of distance from the source and correctly represent the near-source diffusion in weak winds. The performances of the model were evaluated against the field experiments carried out at the Idaho National Engineering Laboratory and during the convective conditions at the Indian Institute of Technology. Furthermore, the study suggests that the inclusion of the longitudinal diffusion, important at short distance diffusion from a continuous point source in low wind conditions, can improve the description of the turbulent transport of atmospheric contaminants.