5.6
Vertical dispersion at short-range from near-ground continuous sources in a neutral boundary layer
Rex Britter, University of Cambridge, Cambridge, United Kingdom; and S. R. Hanna
The short-range vertical dispersion of a passive contaminant in a neutrally-stratified turbulent boundary layer from a near-ground continuous source can be characterized by a number of approaches, such as a vertical Gaussian dispersion parameter sz, a vertical diffusivity Kz, and a vertical entrainment velocity, we. we is proportional to d(sz)/dt. While the Gaussian model is widely used in most air quality applications, the vertical entrainment formula is widely used in fluid modeling studies and in models for vertical dispersion of hazardous gases. This paper summarizes experiments in three fluid model facilities (two in the U.S. and one in the UK), which lead to the conclusion that the entrainment coefficient a in the formula we=au* is a=0.65 ± 0.05. This result is consistent with a recent reanalysis of the Prairie Grass field data, which gave a=0.65 ± 0.05. These empirical assumptions are consistent with scientific knowledge and data and also lead to an a of about 0.6 or 0.7.
Session 5, concentration fluctuations, model uncertainty and evaluation
Wednesday, 22 May 2002, 9:00 AM-1:30 PM
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