The influence of an obstacle on flow and pollutant dispersion in neutral and stable boundary layers
The influence of an obstacle on flow and pollutant dispersion in neutral and stable boundary layers
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DOI：
10.1016/j.atmosenv.2015.05.016
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发表时间：
2015-07
影响因子：
5
通讯作者：
J. Tomas;M. Pourquié;H. Jonker
中科院分区：
文献类型：
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作者：
J. Tomas;M. Pourquié;H. Jonker
预测污染物在城市环境中的扩散需要精确处理障碍物几何形状、流入湍流和温差。本文考虑了热分层和单一障碍物的存在对湍流边界层中污染物扩散的影响。采用大涡模拟的方法，模拟了具有线状污染源的围栏上的湍流流动。进行了单独的“驱动程序”模拟，以生成不同分层水平的流入TBL。利用这些流入TBLs，研究了栅栏后高达100栅栏高度h的流动发展和污染物扩散。结果表明，速度和温度缺陷的衰减与稳定性无关，而雷诺数应力和浓度过剩的衰减随稳定性的增加而减小。在中性情况下，障碍物的影响在大约75h后消失，而在接近地面的稳定情况下，与未受干扰的情况相比，流动仍然加速。栅栏确实会导致局部分层减少，从而增加污染物的扩散。然而，在最稳定的情况下，忽略浮力的影响会导致在排放源下游75小时处污染物浓度被低估2.5倍。
Predicting pollutant dispersion in urban environments requires accurate treatment of obstacle geometry, inflow turbulence and temperature differences. This paper considers both the influence of thermal stratification and the presence of a single obstacle on pollutant dispersion in turbulent boundary layers (TBLs). Turbulent flow over a fence with line sources of pollutant in its vicinity is simulated by means of Large-Eddy Simulations. Separate ‘driver’ simulations are done to generate the inflow TBL for several levels of stratification. Using these inflow TBLs the flow development and pollutant dispersion behind the fence, up to 100 fence heights,h, is investigated. It is shown that the decay of velocity and temperature deficit is independent of stability, while the decay of Reynolds stress and concentration excess decreases with increasing stability. For neutral cases the influence of the obstacle is gone after approximately 75h, while for stable cases near the ground the flow is still accelerated compared to the undisturbed case. The fence does cause a local reduction of stratification and thereby increased pollutant dispersion. However, neglecting the effect of buoyancy results in an underestimation of pollutant concentration by a factor 2.5 at 75hdownstream of the emission source for the most stable case.