Comments on “Lateral Dispersion from Tall Stacks”

Abstract

A few minor errors in a paper by Hanna are noted and several questions are raised about apparent inconsistencies. One question is why substantial enhancement of σy, by buoyancy was noted for the Bull Run data but was unmentioned for the Kincaid data; information given in the paper suggests similar ranges of X*/F* at both plants, but much smaller F* values at Kincaid, which may account for the lack of noticeable buoyancy effects there. The inconsistency between the recommended equation σy/x = 0.6 w*/u and the σy/x values recommended for various stability classes (based on u/w* ranges) can be removed by multiplying this σy expression by a factor which accounts for the effect of mechanical turbulence. Finally, it is noted that an identical equation was recently reported to give a good fit to σy from passive sources released above 0.3 h, albeit to much smaller distances than reported by Hanna.