Flow pattern and pollutant dispersion over three dimensional building arrays. (September 2015)

• Record Type: Journal Article
• Authors: Shen, Zhi; Wang, Bobin; Cui, Guixiang; Zhang, Zhaoshun
• Is Part Of: Atmospheric environment. Volume 116(2015)
• Page Start: 202
• Page End: 215
• Publication Date: 2015-09
• Subjects: Large-eddy-simulation -- Urban canopy -- Pollutant dispersion -- Flow pattern; Air -- Pollution -- Periodicals; Air -- Pollution -- Meteorological aspects -- Periodicals; 551.51
• DOI: 10.1016/j.atmosenv.2015.06.022
• Languages: English
• ISSNs: 1352-2310

Abstract

Abstract: The flow pattern and pollutant dispersion in urban canopies is investigated by large eddy simulation of flow over an array of cubes. It had been found that the pattern of flow over an isolated cubical obstacle can be characterized by an external wake of horseshoe vortex around the lower part of the windward face and an internal wake of recirculation cavity leeward. The width of the external wake W ex and the size of the internal wake L in in the isolated roughness flow are used as key parameters to determine the wake effects on the flow and dispersion in the canopy of the same roughness height h in the isolated roughness flow. Flow patterns are categorized into five types based on the packing density as a result. The five types of urban canopy flow are introduced as (1) Isolated roughness flow when the lateral building interval W L is much greater than W ex and the streamwise building interval W S is much greater than L in ; (2) External wake interference flow when W L is less than W ex while W S is greater than L in ; (3) Internal wake interference flow when W S is in the same order of the size of L in ; (4) Skimming flow when W L is less than W ex and W S is less than L in (5) Street network flow when W L and W S are much less than the W ex and L in respectively. Results of time-averaging velocity field and pollutant concentration contours are demonstrated for each type of flow patterns. It is concluded that the behavior of flow pattern and pollutant dispersion is governed by the packing density from a very low packing density case, approximated as the flow around an isolated roughness element, to a high packing density case, resembled as the network flow. Highlights: Accomplishment of LES investigation of flow and pollutant dispersion in building arrays. Discovery of five identifiable flow patterns which is closely related to building density. Exploration of the relationship between flow patterns and pollutant dispersion.