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| Impact of wall heating effects on pollutant dispersion in urban street canyon. |
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Abstract The software Fluent was used to simulate wind field and pollutant concentration distribution under different wall heating condition in the urban street canyon. Under the ratio of the street height to width (H/W) was 1.33 and the low wind speed conditions (u=1m/s), when there was no temperature difference between the wall and the ambient air, a big stable clockwise vortex was existed in the street canyon, and pollutant accumulated on the leeward side. If the leeward side was heated or the ground surface and leeward side were heated together, the air flow distribution was similar to the case of no temperature difference in the canyon, and the pollutant concentration decreased due to the increased turbulence intensity in the canyon. While the windward wall was heated, the single vortex structure in the canyon was changed into double-vortices structure. There was high pollutant concentration in low of the canyon and low pollutant concentration in upper of the canyon. When the ground surfaces and windward wall were heated simultaneously, the flow structure in the canyon was changed from single vortex into double-vortices structure under small temperature difference in the street canyon (Δθ=2℃). While increased the temperature difference to 5℃, the double-vortices in the canyon were broken down into three vortices, and the pollutant distribution was similar to windward wall heated condition. The simulated result of Fluent was reasonable through the comparison of measured concentration and simulated concentration.
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Received: 06 January 2009
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