Urban wind fields are of concern because the near-ground wind vector drives the ventilation of cities, which involves, among other things, the translocation and dilution of air pollutants. To study flow patterns in the urban atmospheric boundary layer, turbulence-resolving tools are needed since numerous roughness elements are present that cause the flow to be of highly turbulent nature. Therefore, we developed a mobile, fast-response measurement platform that is situated on a cargo bicycle. This mobile platform was deployed in a case study collecting data at street level within a complex, urban area that includes street canyons, open squares, street intersections as well as courtyard entrances. Results were compared to numerical large eddy simulation (LES) data from the model PALM. Outcomes of both methods were qualitatively analyzed; results show that both methods were able to identify complex flow patterns, including small-scale structures such as jetting flows, vortices, recirculation areas, and a convergence zone where air masses collide. Results of both methods generally matched well, even for areas that featured highly complex, three-dimensional flow structures. We conclude that both the model PALM and the mobile platform are valuable tools for gathering insights about complex flow structures in real-world environments.

中文翻译：

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分析街道峡谷中的湍流风场：LES模型结果与来自移动平台的数据之间的良好一致性

城市风场之所以令人关注，是因为近地面风矢量驱动了城市的通风，其中包括空气污染物的转移和稀释等。为了研究城市大气边界层中的流动模式，需要湍流解析工具，因为存在大量的粗糙元素，这些元素会导致流动具有高度湍流的性质。因此，我们开发了一个移动的，快速响应的测量平台，该平台位于货运自行车上。在案例研究中部署了此移动平台，该案例研究收集了复杂的市区内街道水平的数据，包括街道峡谷，开放广场，街道交叉口以及庭院入口。将结果与模型PALM的数值大涡模拟（LES）数据进行比较。定性分析了两种方法的结果。结果表明，这两种方法均能够识别复杂的流动模式，包括小规模结构，如喷射流，涡流，再循环区域以及气团碰撞的汇聚区。即使对于具有高度复杂的三维流动结构的区域，这两种方法的结果通常也很好地匹配。我们得出结论，模型PALM和移动平台都是用于收集有关现实环境中复杂流结构的见解的有价值的工具。