| 摘 要： | 采用CFD软件Fluent研究了不同壁面加热条件下街道峡谷内流场及污染物浓度分布情况.结果表明,当街道高宽比(H/W)为1.33时,在低风速(u=1m/s)条件下,当壁面与周围大气无温差时,街道峡谷内存在一个稳定的顺时针大漩涡,污染物在背风侧堆积.当背风面、地面和背风面分别被加热时,峡谷内流场分布与无温差时相似,此时峡谷内的湍流强度增强,导致污染物浓度降低.当迎风面被加热时,峡谷内流场由原来的单漩涡结构变为双漩涡结构,此时街道峡谷下部浓度较高,上部浓度相对较低.当地面和迎风面同时被加热,温差较小(?θ=2℃)时,街道峡谷内流场由单漩涡结构变为双漩涡结构; 温差增大为5℃,峡谷内由双漩涡分裂成了3个漩涡,此时污染物分布与迎风面被加热情况相似.通过实测值和模拟值的比较可知,Fluent软件对街道峡谷大气环境的模拟结果基本合理.
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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. |
