• 关键词：城市街谷  双层高架桥  数值模拟  污染物浓度分布

• 基金项目：国家自然科学基金（No.51678058）

• 秦成君
• 太原理工大学环境科学与工程学院, 太原 030024

• 宋翀芳
• 太原理工大学环境科学与工程学院, 太原 030024

• 王世杰
• 太原理工大学环境科学与工程学院, 太原 030024

• 赵敬源
• 长安大学建筑学院, 西安 710061

• 摘要：城市街道中复杂的高架桥结构会影响街谷内污染物的扩散.本文利用CFD软件FLUENT，采用标准k-ε方程和组分输运方程，对含双层高架桥的理想街谷内空气流场和CO浓度场进行了数值模拟.结果表明，高架桥破坏了理想街谷内CO浓度分布的爬墙效应，自地面沿高度方向CO浓度逐渐减小，超过每层高架桥面后激增，而后再次降低.双层高架桥改变了污染面源位置和街谷内流场分布.当双层高架桥都处于街谷内部时，来流风垂直于街谷方向自左向右吹送，街谷内涡旋整体结构保持顺时针方向，高架桥附近出现小涡旋，使得CO在街谷内部循环，引起背风面和街谷内CO平均浓度的升高，高架桥的"盖子效应"显著，与无高架桥街谷相比，CO平均浓度升高39.5%.当双层高架的上层高架与街谷建筑顶部持平，下层高架桥位于街谷中部时，街谷内部产生4个较大涡旋，能够显著地提高街谷内地面和背风面CO扩散速率，高架桥的"盖子效应"被破坏；与无高架桥街谷相比，CO平均浓度仅升高8.7%，与双层高架桥都处于街谷内相比，CO平均浓度降低22.1%，为城市多层高架桥建设提供了参考依据.

• Abstract：The complex viaduct structures in urban streets affect the spread of pollutants in street streets. Used CFD software FLUENT, the standard k-ε equation and component transportation equation were used to simulate the characteristics of air flow field and CO concentration field in the street canyon with double viaduct layout. The results showed that when the viaduct was located in the street canyon, the viaduct destroyed ‘climbing wall effect’ of the concentration distribution of CO in the ideal street. The concentration of CO decreased along the height from the ground surface and increases sharply after exceeding the viaduct. The existence of double viaducts changed the location of surface pollution sources and the distribution of flow field in the street canyon. When the double viaducts were all inside the street canyon, the overall structure of the vortices in the street canyon keeps a clockwise direction, and small vortices appear near the viaduct, causing CO to circulate inside the street canyon, causing an increase in the mean CO concentration in the leeward side and in the street canyon, the "cover effect" of the viaduct was significant, and the average concentration of CO was 39.5% higher than that of the viaduct without the viaduct. When the height of the double-storey overhead was the same as the height of the top of the street canyon, four large vortices were generated in the street canyon, which can significantly increase the CO diffusion rate in the street canyon, and the CO concentration increased only compared with that of the viaduct street canyon 8.7%. Compared with the double viaducts in the street canyon, CO concentration decreased by 22.1%, which provided a reference for the construction of urban multi-viaduct.

• Key words：city street canyon  double viaduct  numerical simulation  concentration distribution of pollutant

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