15.2
Influence of urban morphology on street level concentration: Water channel and field study in three Southern Californian Cities
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From the field experiments that we carried out in these three urban areas, it was found that traffic load in arterials is less important compared with the influence of surrounding building arrangements on street level concentrations of pollutants, so in this study, we investigated the plume dispersion from three levels of source strength for each urban area. Finally, we compared the nondimensional concentration C*=CuH2/Q (where C is the concentration of pollutant [mg/m3], u is the free stream velocity [m/s], H is the characteristic length [m] taken as the average building height, and Q is the pollutant emission rate [mg/s]) of plume 1) for each building arrangement with varying source strength and 2) for the same source strength through different building arrangements. Mean velocity, turbulence intensity, mean concentration and concentration fluctuation intensity were compared for all cases.
In order to understand the variation of turbulent and plume structures for different building arrangements, the integral turbulent length scale Lχ was estimated from the velocity spectrum and the integral time scale of concentration fluctuations Tχ was calculated. The values of Lχ and Tχ for three urban areas in water channel were reported and compared. The influence of building configurations and the physical mechanisms governing ground level concentrations will be presented.