Analysis of Pollutant Entrainment from Localized Sources in a Street Network

The propagation of a pollutant emitted from localized sources both within and above regular street network is studied by analyzing data direct numerical simulations passive scalar dispersion. Two wind directions are considered, corresponding to aligned oblique flow with respect the axes. Particular attention paid role entrainment into urban canopy an elevated source re-entrainment material originally released further upstream ground source. variation concentration differences vertical fluxes between streets air as function distance reveals important rate lateral mixing for two sources. Detrainment need longer fetch equilibrate than There large advection detrainment velocities cases, so that change in direction could affect ventilation efficiency considerably. Time scales associated different dispersion processes computed time first appearance onset release mapped. It shown can provide shortcut pathway reaching certain parts network. This particularly striking case flow, when be transferred up twice rapidly advection. Taken together, these results highlight overall message exchange two-way process needs considered context emergency response well ventilation.