A Model of Plume Advection Velocity for Dispersion in Urban Arrays
In the basic Gaussian plume model (GPM) used for predicting concentrations due to continuous plume releases, the mean concentrations in the plume are inversely proportional to the mean plume advection speed Up. For elevated releases, Up is evaluated at the height of the release or some other representative height. For ground level releases in a shear layer, Up varies with distance from the source, since as the plume grows vertically in the boundary layer, it encounters progressively higher wind speeds. From similarity theory, it is possible to show that the correct wind speed to use in this case is Up ≈ U(0.5σZ), that is to say the wind speed evaluated at approximately one half the plume vertical standard deviation.
KeywordsWind Tunnel Urban Canopy Plume Height Ground Level Concentration Obstacle Array
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