A WIND-TUNNEL EXAMINATION OF THE VARIATION OF SIGMA-Y AND SIGMA-Z WITH SELECTED PARAMETERS

Wind-tunnel tests were conducted to examine how sigma(y) and sigma(z) (the standard Gaussian dispersion parameters) might be expected to var y with source height and downwind distance, both with and without the presence of several building configurations. For isolated sources, the re was no discernible effect of release height on sigma(y), but in con trast there appeared to be a dependence of sigma(z) on source height. The effect of buildings was dependent on the particular configuration, and in general sigma(y) and sigma(z) appeared to be affected differen tly. Particularly significant effects were observed for cases when the plume was directed at an oblique angle to the buildings. For releases less than the building height there was no effect of release height o n sigma(y) and sigma(z). It was also observed that for a stack 3.5-tim es the average building height, sigma(y) was still significantly affec ted by the presence of the building array.