The
Attribution of Pollutant Concentrations on Buildings from Local Traffic
– Effects on Ventilation Requirements.
A Wind Tunnel Modelling Study
D.J. Hall*,
H. Sharples**, S. Walker***, V. Kukadia****.
BRE, Garston,
Watford WD25 9XX, UK.
* BRE
Associate & Envirobods Ltd. **
Now BAE Systems Ltd.
*** Now Dstl Porton Down. **** BRE Ltd.
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Abstract
This paper describes an analysis using the BRE
Pollution Dispersion Wind Tunnel to estimate pollution concentration
patterns on buildings in urban arrays due to local ‘line’ sources of
pollution, typical of vehicular traffic emissions. The experimental
procedure involved measurements of both pressure and concentration
patterns on building forms in urban arrays, intended to provide
information on the ingestion of pollutants into buildings in urban areas.
A series of individual contaminant sources was used to represent the line
source so that the spatial contribution of each part of the line source to
the total exposure could be identified. Two line sources were considered:
one of which was directly next to a test building located in the urban
array and a second, which was located one street away.
It was possible to
estimate from the measurements the regions of building faces that would be
acceptable or otherwise as locations for air intakes for natural or
mechanical ventilation. In the former case, regions of relatively high
pressure and low contaminant concentration are required at low levels
around the building. The results were used to assist in providing guidance
on determining acceptable ventilation air intake placement for both
natural and mechanical systems. The placement of air intakes was found to
be critical for a line source placed directly adjacent to the test
building. For this situation the only suitable location to minimise the
ingress of traffic pollutant was at high level. However, for buildings
located only one or two streets away, surface concentrations were found to
be relatively uniform and hence, with respect to vehicle emissions, the
placement of intakes was considered to be less critical.
Key words: Wind tunnel, line sources, traffic pollution, air
intake placement, urban areas.
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