Loading…
Dense gas vertical diffusion over rough surfaces: results of wind-tunnel studies
A cooperative program of measurements of vertical diffusion of continuous, dense gas plumes over rough surfaces in neutral boundary layers has been carried out in three wind tunnels in the USA and the UK. The three environmental boundary layer tunnels were at the Chemical Hazards Research Center (CH...
Saved in:
Published in: | Atmospheric environment (1994) 2001-01, Vol.35 (13), p.2265-2284 |
---|---|
Main Authors: | , , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
Summary: | A cooperative program of measurements of vertical diffusion of continuous, dense gas plumes over rough surfaces in neutral boundary layers has been carried out in three wind tunnels in the USA and the UK. The three environmental boundary layer tunnels were at the Chemical Hazards Research Center (CHRC) at the University of Arkansas, the Fluid Modeling Facility (FMF) of the US Environmental Protection Agency in North Carolina, and the Environmental Flow Research Centre (EnFlo) at the University of Surrey. A simple and consistent set of definitions was adopted for the plume variables like plume depth, mean plume transport speed, vertical entrainment velocity,
w
e, and plume Richardson number
Ri
∗
, where
Ri
1/2
∗
is a ratio of buoyancy-induced flow velocities to
u
∗
, the upstream-of-source ambient friction velocity. The present experiments focus on how
Ri
∗
affects the ratio
w
e
/u
∗
. In order to maintain nearly constant
Ri
∗
in distance and time, continuous line sources of dense gas, primarily CO
2, were employed. Good agreement was found among the three tunnels. The results also agree with the classic Prairie grass field experiment for the “passive limit” (
Ri
∗
=0):
w
e
/u
∗
=0.6–0.7. For
Ri
∗
up to 20, the results fit the equation
w
e
/u
∗
=0.65/(1+0.2
Ri
∗
). For
Ri
∗
>20, molecular diffusion and viscosity effects were apparently quite strong because
w
e was observed to collapse to values nearly commensurate with molecular diffusion alone. |
---|---|
ISSN: | 1352-2310 1873-2844 |
DOI: | 10.1016/S1352-2310(00)00360-5 |