Large‐eddy simulation of vortex streets and pollutant dispersion behind high‐rise buildings
Large‐eddy simulation of vortex streets and pollutant dispersion behind high‐rise buildings
复制标题
高层建筑背后涡街与污染物扩散的大涡模拟
DOI：
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
K. Kwak
中科院分区：
文献类型：
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作者：
B. Han;Seung;Jong‐Jin Baik;Junho Park;K. Kwak
了解城市地区的湍流和污染物扩散是城市气象学和环境流体力学的重要问题之一。在这项研究中，我们研究湍流和污染物扩散在一个密集的建成区在首尔，韩国，使用并行大涡模拟模型（PALM）。特别是，我们专注于涡街道和相关的污染物扩散背后的高层建筑。湍流再循环方法用于产生入流剖面。在高层建筑物附近产生涡流，并向下游传播，在高层建筑物后面形成涡街。为了研究涡街的特性，进行了谱分析和相关分析。频谱分析表明，旋涡具有0.1-0.2的无量纲旋涡脱落频率，并且由于其他建筑物的影响，这种周期性被削弱。相关分析表明，在负压扰动区，涡的出现频率较高。由喷射和扫掠引起的垂直湍流动量通量对高层建筑下游的总垂直湍流动量通量有很大贡献。特别是，尾流区域的喷射比其他区域更强，因为喷射是由高层建筑顶部附近的涡流引起的。研究发现，污染物的扩散被低层和高层建筑物打断。高层建筑后面的强烈上升气流将污染物向上输送，并增加上层的平均污染物浓度。形成涡旋街道的涡旋在污染物混合中发挥作用，使得涡旋将高污染物浓度的空气从高层建筑物后面的尾流区喷射出来，并将低污染物浓度的空气带入尾流区。涡量与污染物浓度的相关性证实了涡的混合作用。
Understanding turbulent flow and pollutant dispersion in urban areas is one of the important problems in urban meteorology and environmental fluid mechanics. In this study, we examine turbulent flow and pollutant dispersion in a densely built‐up area in Seoul, South Korea, using the parallelized large‐eddy simulation model (PALM). In particular, we focus on vortex streets and associated pollutant dispersion behind high‐rise buildings. The turbulence recycling method is used to produce inflow profiles. Vortices are generated near the high‐rise buildings and propagate downstream forming vortex streets behind the high‐rise buildings. To investigate characteristics of the vortex streets, spectral and correlation analyses are performed. The spectral analysis reveals that vortices have a non‐dimensional vortex shedding frequency of 0.1–0.2, and this periodicity is weakened due to the influence of other buildings. The correlation analysis shows that vortices appear frequently in regions of negative pressure perturbation. The vertical turbulent momentum fluxes induced by ejections and sweeps largely contribute to the total vertical turbulent momentum flux downstream of the high‐rise buildings. Especially, ejections in the wake region are stronger compared to other regions because ejections are induced by vortices near the top of the high‐rise buildings. It is found that pollutant dispersion is interrupted by both low‐rise and high‐rise buildings. Strong updraughts behind the high‐rise buildings transport pollutant upward and increase the mean pollutant concentration at upper levels. Vortices forming the vortex streets play a role in pollutant mixing in such a way that the vortices eject air of high pollutant concentration from the wake region behind the high‐rise buildings and entrain air of low pollutant concentration into the wake region. The mixing by vortices is verified by the correlation between vorticity and pollutant concentration.
影响因子：
5
作者：
Letzel, Marcus Oliver;Krane, Martina;Raasch, Siegfried
通讯作者：
Raasch, Siegfried