城市高架道路对微尺度湍流和空气污染物扩散的影响

Plenty of viaduct settings have been constructed in urban area since the rapid development of urbanization. Due the existence of urban viaducts, characteristics of the turbulence and pollutants’ dispersion in micro-environment is affected. Therefore, huge concentration gradients of the air pollutants exist nearby the viaducts, which produce more difficulties for observation and simulation. In this project, scale-model idealized urban models with viaduct model units and controllable emission sources will be constructed in the suburban area of Guangzhou. The model unit are flexible in controlling building thermal properties, easily measurable for building thermal storage. The high-quality field monitoring campaigns with these scale-model idealized urban models will be performed to validate and improve the dispersion simulation of Lagrangian Particles Model (LPMs) in micro scale. By scale-model monitoring and LPMs modelling, this study will quantitatively evaluate the impact of urban viaduct settings on the characteristics of turbulence and pollutants’ dispersion in micro scale. Scenarios of the viaduct in street canyons with different height/width ratios will be considered both in scale-model observation and LPMs simulation. Field Observation in real urban areas with viaducts will be implemented, using to improve the LPMs simulation in real community with viaduct. The impacts of the viaduct on the dispersion and the exposure concentration of local air pollutants will be evaluated with different weather condition, emphatically with stable weather condition. The systematic research in this project will approach further cognition of micro-scale turbulence and dispersion. It would be absolutely beneficial to the improvement of non-steady numerical simulation, and the urban micro-climate planning for sustainable cities. Furthermore, this research will be the key point of discipline-crossing of atmospheric chemistry and exposure science.

随着城市化而大量修建的高架道路，影响城市微环境湍流及污染物扩散特征，使污染物浓度空间变异极大，给观测实验和模式模拟带来挑战。本项目拟在广州郊区建立热力参数与排放源可控、建筑热通量易测的理想城区及高架道路模型，通过高质量的缩尺尺度模型外场实验，在其验证下提高拉格朗日粒子扩散模式（LPMs）微尺度数值模拟的准确性，并将两者结合，定量研究城市高架道路这一特殊城市形态，在不同高宽比（H/W）的城市街谷中，对微尺度湍流及污染物扩散特征的影响机理。通过缩尺尺度外场实验优化模式参数，提高模拟效果，通过实际城区高架道路外场观测，完善LPMs对真实高架道路污染物扩散的模拟，并着重探讨典型天气和静稳天气条件下高架道路对局地污染物扩散和暴露浓度分布的影响。相关研究有利于深入认知微尺度湍流和扩散特征，有助于改进非稳态数值模拟方法和推进可持续性城市微气候规划，并可成为联结大气化学和暴露科学研究之间的桥梁。

高架道路等城市建筑布局结构，影响城市微环境湍流及污染物扩散特征，使污染物浓度空间变异极大，给观测实验和模式模拟带来挑战。本项目在广州郊区建立了热力参数与排放源可控、建筑热通量易测的理想城区模型，配合绿化模型，建筑通风模型、高架道路模型等，进行了非稳态边界条件下的高质量缩尺尺度模型外场实验和可控排放源扩散实验。基于缩尺尺度实验和风洞实验，验证并优化拉格朗日粒子扩散模式（LPMs）和CFD模式，提高微尺度数值模拟的准确性。此外本研究还在广州城区搭建了高时间分辨率的城市风温湿与空气污染精细观测网，对真实城区的风温湿环境和污染要素进行长期定点观测。在此基础上，本研究结合观测和模拟，定量研究城市绿化、高架道路、城市街谷等多种城市形态，对微尺度湍流及污染物扩散特征的影响机理。通过一系列研究，本项目建立了一整套观测、模拟和评估真实社区污染物扩散以及居民曝露研究的方法，充分探讨了街谷高宽比、太阳辐射对街谷湍流结构的影响；室内外温差和通风方案对室内外流场、建筑自然通风和污染物扩散的影响；二维街谷中涡流的雷诺独立性研究；机械力和热浮力共同作用下街谷通风及街谷内部单元之间的扩散特征；街谷高宽比和城市绿化方案对街谷风热环境的影响。这些工作深刻分析探讨了城市建筑环境中风热环境的关键影响要素和影响机理，在此基础上建立了一整套有机的整体研究方法，将大气科学数值模式的应用，拓展联结到暴露科学，为大气科学与环境科学、公共卫生等领域的学科交叉，提供了重要的科学参考。这些工作同时也为可持续性城市气候规划提供了重要参考。

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