Use of point source models for the dispersion of releases of finite size

Abstract

If the releases are of finite size, the point source model is widely accepted as an approximation to the concentration in the far field. However, substantial improvement upon the point source model can be achieved by shifting the origin of the point source release to a virtual origin, a point upwind of the origin of the finite size release. In this paper, rigorous solutions for the finite size release models are compared against the point source model to determine the optimum virtual origin shift so as to produce the most accurate approximation in the intermediate and far fields. Also, the effects of anisotropic diffusion are considered in order to model atmospheric diffusion more closely.