汞蒸气在参差建筑街区中沉积过程模拟

利用计算流体动力学方法,分别选用参差比为0.0, 0.2, 0.4, 0.6和0.8等5种建筑模型,探讨了在水平自然风条件下重密度污染源(汞)在不同参差比建筑物间的沉积过程,以及街区内行人层汞浓度与建筑参差比之间的关系.模拟结果发现,城市街区建筑物高低错落分布的布局会促进高空汞污染源在行人层的聚集,使得街区行人层汞浓度明显增大;并且随着街区建筑物参差比的增大,最高汞浓度值所在的街道有序地靠近来流上游,而较高建筑物背风面街道行人层汞质量流量明显高于较矮建筑物背风面街道行人层汞质量流量.

Numerical modeling of mercury vapour dispersion and sedimentation within the urban building street canyons composed by diverse building heights

With the use of computational fluid dynamics, dispersion and accumulation of Hg inside the street canyons with various building heights were numerically investigated, concerning with neutral thermal stratifications and five canyon deviations, 0.0, 0.2, 0.4, 0.6, and 0.8. Particularly, correlations between building height variation and pedestrian level pollutant accumulation were established depending on the discrete numerical simulations. Numerical simulations indicate that high altitude Hg pollutants were inclined to accumulate in the region of pedestrian level due to the enhanced street canyon building height variations, Hg concentration in the region of pedestrian level therefore significantly increased. Furthermore, street canyons of peak Hg concentrations usually were sequentially allocated along the wind flows, maximum one mostly closing the upwind side. Hg fluxes in the street canyons of high-rise buildings backward were observed to be significantly higher than those in the street canyons of low-rise buildings backward.