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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
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. = Turbulent image - Instantaneous image Average image (Cavg)