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CONCENTRATION FLUCTUATIONS IN URBAN STREET CANYON POLLUTANT DISPERSION PowerPoint Presentation
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CONCENTRATION FLUCTUATIONS IN URBAN STREET CANYON POLLUTANT DISPERSION - PowerPoint PPT Presentation


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CONCENTRATION FLUCTUATIONS IN URBAN STREET CANYON POLLUTANT DISPERSION. Background. Pollutant concentration fluctuations are important in assessing toxic risk to people in urban street canyons. However, experimental data within typical building arrays is very limited. Vehicle exhaust.

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CONCENTRATION FLUCTUATIONS IN URBAN STREET CANYON POLLUTANT DISPERSION

Background

Pollutant concentration fluctuations are important in assessing toxic risk to people in urban street canyons. However, experimental data within typical building arrays is very limited.

Vehicle exhaust

Objective

It has been suggested that the r.m.s. fluctuations (Crms) are of the order of the mean values. However, such estimates vary greatly. We aim to quantify the relationship through a lab study.

An urban street canyon with traffic

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Research Being Carried Out

Various obstacle arrays have been studied in a large hydraulic flume. Concentration distribution time-histories in a series of canyons downstream of a single source have been measured using Planar Laser Induced Fluorescence (PLIF).

Key Findings

The first data show thatCrms in the shear layer above the array is of the order of the mean(Cavg). The peak of the relative intensity (Crms/Cavg) also occurs here and can exceed unity in canyons immediately downstream of the source.

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Turbulent

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Instantaneous image

Average image (Cavg)