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首页> 外文期刊>Atmospheric environment >Passive urban ventilation by combined buoyancy-driven slope flow and wall flow: Parametric CFD studies on idealized city models
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Passive urban ventilation by combined buoyancy-driven slope flow and wall flow: Parametric CFD studies on idealized city models

机译：由浮力驱动的坡面流和墙体流相结合的被动城市通风：理想城市模型的参数CFD研究

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摘要

This paper reports the results of a parametric CFD study on idealized city models to investigate the potential of slope flow in ventilating a city located in a mountainous region when the background synoptic wind is absent. Examples of such a city include Tokyo in Japan, Los Angeles and Phoenix in the US, and Hong Kong. Two types of buoyancy-driven flow are considered, i.e., slope flow from the mountain slope (katabatic wind at night and anabatic wind in the daytime), and wall flow due to heated/ cooled urban surfaces. The combined buoyancy-driven flow system can serve the purpose of dispersing the accumulated urban air pollutants when the background wind is weak or absent. The microscopic picture of ventilation performance within the urban structures was evaluated in terms of air change rate (ACH) and age of air. The simulation results reveal that the slope flow plays an important role in ventilating the urban area, especially in calm conditions. Katabatic flow at night is conducive to mitigating the nocturnal urban heat island. In the present parametric study, the mountain slope angle and mountain height are assumed to be constant, and the changing variables are heating/cooling intensity and building height. For a typical mountain of 500 m inclined at an angle of 20° to the horizontal level, the interactive structure is very much dependent on the ratio of heating/cooling intensity as well as building height. When the building is lower than 60 m, the slope wind dominates. When the building is as high as 100 m, the contribution from the urban wall flow cannot be ignored. It is found that katabatic wind can be very beneficial to the thermal environment as well as air quality at the pedestrian level. The air change rate for the pedestrian volume can be as high as 300 ACH.
机译：本文报告了对理想城市模型进行参数CFD研究的结果，以研究在没有背景天气时，坡地通风对山区城市通风的潜力。这样的城市的例子包括日本的东京，美国的洛杉矶和凤凰城以及香港。考虑了两种类型的浮力驱动的流动，即，来自山坡的斜坡流（夜间的喀巴特风和白天的绝热风）以及由于加热/冷却的城市表面而产生的壁流。当背景风微弱或不存在时，组合式浮力驱动流系统可用于分散累积的城市空气污染物。根据换气率（ACH）和空气年龄评估了城市结构内通风性能的微观图像。仿真结果表明，斜坡流在市区通风中起着重要作用，尤其是在平静的条件下。夜间的白沙流有利于缓解夜间的城市热岛。在本参数研究中，假定山坡角和山高是恒定的，并且变化的变量是加热/冷却强度和建筑物高度。对于一个典型的500 m的山峰，它与水平面成20°的角度倾斜，交互结构在很大程度上取决于供暖/制冷强度之比以及建筑物的高度。当建筑物低于60 m时，倾斜风占主导地位。当建筑物高至100 m时，城市壁流的贡献不容忽视。已经发现，合成风对行人水平的热环境以及空气质量都非常有益。步行者的换气率可能高达300 ACH。

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  • 来源
    《Atmospheric environment》 |2011年第32期|p.5946-5956|共11页
  • 作者

    Zhiwen Luo; Yuguo Li;

  • 作者单位

    Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, SAR, China;

    Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, SAR, China;

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  • 原文格式 PDF
  • 正文语种 eng
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  • 关键词

    slope flow; ventilation; street canyon; age of air; wall flow;

    机译：边坡流量通风;街头峡谷空气年龄壁流;

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