Concentration fluctuation studies of plume dispersion for different release heights in the convective boundary layer

The prediction of spatial and temporal distribution of contaminants released from a localized source is of considerable interest for air pollution studies. Concentration fluctuations occur due to the turbulent nature of pollutant dispersion in the atmosphere. Short term concentration fluctuations data can provide valuable information, such as the concentration peak values and toxicity levels. However, the dependency of the random concentration field on various factors, such as source and turbulence characteristics, is not clearly understood. Using Large Eddy Simulation, it is possible to study the concentration fluctuation field of a dispersing plume in the atmosphere. A large eddy model calculates the large scale turbulent motion by solving the filtered Navier-Stokes equation for the large scale. With increase in the grid resolution, results from the large eddy simulation will approach the direct numerical simulation results and reveal the fluctuations characteristics. In this study, high resolution Large Eddy Simulation (LES) is used for studying the dispersion of a non-buoyant passive scalar in the convective boundary layer at various release heights. Concentration fluctuation statistics such as peak values, intermittency and probability density function are reported. Some of the mean and fluctuations statistics are compared with the experimental and numerical results reported in the literature.

* Present Address: Titan Corporation, Arap group, P.O Box 2229, Princeton, NJ 08543-2229