United States Department of Transportation
i
Modifications of highway air pollution models for complex geometries, volume II : wind tunnel test program.
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2002-09-01
[PDF-10.53 MB]
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Edition:Final report vol. II; Sept. 1984-July 1989.
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Abstract:This is volume I1 of a two-volume report of a study to increase the scope and clarity of air pollution models for
depressed highway and street canyon sites. It presents the atmospheric wind tunnel program conducted to increase the
data base and improves physical concepts of pertinent movements and mixing of air and its contaminants. Wind tunnel
measurements are less costly than field measurements and are sensitive to controlled input variables.
The f~swti nd tunnel operations assured geometric, vortex structure, and upstream flow similarity and correct
building wake and moving vehicle effects. Tracer gases from point, line, and moving vehicle sources were used
appropriately. For wind tunnel models of depressed roads or street canyons hot-wire anemometer velocity and turbulence,
pressure distribution and receptor point concentration measurements were made. Using a selected standard road model
which had two dimensions and a width/ height (W/H) ratio of one effects of wind angle, local source location, added
upwind cuts, vehicle speed, ambient wind speed, and the presence of upwind wall canopy were observed. Other
two-dimensional tests involved changing the w/H ratios from 0.25 to 6.0, sloping the walls, slotted walls, walls of unequal
heights, and curved roads. Three dimensional tests included end effects, intersections, and an added taller structure along
one side of the road. Test results gave qualitative evaluations, concise tables, graphic illustrations, and qualitative concepts
of wind flows and dispersion.
Some findings include:
(1) Wind flows and air pollution impacts are affected by W/H ratio, road curvature, and slope of walls, vehicle
movements, and source locations. Slotted buildings upwind reduce impacts.
(2) Air contaminant concentrations are reduced near intersections due to vertical vortices at corners
(3) Simulations of five field sites by wind tunnel tests were satisfactory.
Volume I is publication FHWA-RD-02-036, " Data Analyses and Model Developmenty
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