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The influence of aspect ratios and wall heating conditions on flow and passive pollutant exposure in 2D typical street canyons

机译：纵横比和壁厚条件对2D典型街道峡谷流动和被动污染物暴露的影响

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摘要

Deep street canyons and unfavourable meteorological conditions usually induce high pollutant exposure. Validated by experimental data, this paper employs computational fluid dynamic simulations with RNG k-e model to investigate the flow, and passive pollutant dispersion within scale-model two-dimensional street canyons (H 1/4 3 m). As a novelty, this paper quantifies the impacts of various wall heating scenarios(bottom, leeward/ windward wall and all-wall heating), ambient velocity(Uref 1/4 0.5-2 m s 1, Froude numbers Fr 1/4 0.25-4.08, Reynolds numbers Re 1/4 95602-382409) and aspect ratios(building height/street width, AR 1/4 0.5, 0.67, 1, 2, 3) on personal intake fraction for entire streets(P_IF'). The governing equations are implicitly discretized by a finite volume method (FVM) and the second-order upwind scheme with Boussinesq model for quantifying buoyancy effects. The SIMPLE scheme is adopted for the pressure and velocity coupling. In most isothermal cases, one-main-vortex structure exists as AR 1/4 0.5-3(.P_IF' 1/4 0.43-3.96 ppm and 1.66-27.51 ppm with Uref 1/4 2 and 0.5 m s 1). For non-isothermal cases with Fr 1/4 4.08(Uref 1/4 2 m s 1), winddriven force dominates urban airflow as AR 1/4 0.5-1 and four heating conditions attain similar .P_IF' (0.39-0.43 ppm, 0.57-0.60 ppm, 0.91-0.98 ppm). As AR 1/4 2, windward and all-wall heating get two-vortex structures with greater .P_IF'(3.18-3.33 ppm) than others(.P_IF' 1/4 2.13-2.21 ppm). As AR 1/4 3, leewardwall heating slightly reduces .P_IF'(3.72-3.96 ppm), but the other three produce two-vortex structures with greater .P_IF'(6.13-10.32 ppm). As Fr 1/4 0.25(Uref 1/4 0.5 m s 1), leeward-wall heating always attains smaller .P_IF'(1.20-7.10 ppm) than isothermal cases(1.66-27.51 ppm) as AR 1/4 0.5-3, however the influence of the other three is complicated which sometimes raises or reduces .P_IF'. Overall, smaller background wind speed (Fr 1/4 0.25) with two-vortex structures attains much larger .P_IF'. Special attention is required at night (all-wall heating), noon(bottom-heating) and cloudy period(no-wall heating) as AR 1/4 2-3, while it is during windward-wall heating and cloudy period for AR 1/4 0.5-1.
机译：深街峡谷和不利的气象条件通常诱导高污染物暴露。通过实验数据验证，本文采用与RNG K-E模型的计算流体动态模拟，以研究规模模型二维街道峡谷（H 1/4 3 M）内的流量和被动污染物分散。作为一种新颖，本文量化了各种壁式加热场景（底部，封口/迎风墙和全壁加热），环境速度（尿素1/4 0.5-2 ms 1，Froude Number FR 1/4 0.25-4.08的影响，Reynolds Number Re 1/4 95602-382409）和纵横比（建筑物高度/街道宽度，AR 1/4 0.5,0.67,1,2,3）用于整个街道的个人进气级分（ 0.5-3（.p_if'1/4 0.43-3.96 ppm和1.66-27.51 ppm。对于FR 1/4 4.08（UREF 1/4 2 MS 1）的非等温案例，卷绕力主要占据城市气流作为AR 1/4 0.5-1和四个加热条件达到类似的.p_if'（0.39-0.43 ppm，0.57 -0.60 ppm，0.91-0.98 ppm）。作为AR 1/4 2，迎风和全壁加热使双涡旋结构具有比其他更大的涡旋结构（3.18-3.33 ppm）（.p_if'1/4 2.13-2.21 ppm）。作为AR 1/4 3，Leewardwall加热略微减少.p_if'（3.72-3.96 ppm），但另外三个产生双涡旋结构，具有更大的.p_if'（6.13-10.32 ppm）。如FR 1/4 0.25（尿素1/4 0.5毫秒1），腰壁加热总是比等温案例（1.66-27.51 ppm）持续较小.p_if'（1.20-7.10ppm），如AR 1/4 0.5-3，然而，其他三个的影响是复杂的，它们有时会提高或减少.p_if'。总体而言，具有双涡结构的较小背景风速（FR 1/4 0.25）达到更大的.p_if'。晚上（全壁加热），中午（底部加热）和多云时期（无壁加热）为AR 1/4 2-3，虽然在迎风 - 壁式加热和ar的阴天1/4 0.5-1。

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  • 来源
    《Building and Environment》 |2020年第1期|106536.1-106536.20|共20页
  • 作者

    Hang Jian; Chen Xieyuan; Chen Guanwen; Chen Taihan; Lin Yuanyuan; Luo Zhiwen; Zhang Xuelin; Wang Qun;

  • 作者单位

    Sun Yat Sen Univ Sch Atmospher Sci Guangzhou Peoples R China|Sun Yat Sen Univ Guangdong Prov Key Lab Climate Change & Nat Disas Guangzhou Peoples R China;

    Sun Yat Sen Univ Sch Atmospher Sci Guangzhou Peoples R China|Sun Yat Sen Univ Guangdong Prov Key Lab Climate Change & Nat Disas Guangzhou Peoples R China;

    Sun Yat Sen Univ Sch Atmospher Sci Guangzhou Peoples R China|Sun Yat Sen Univ Guangdong Prov Key Lab Climate Change & Nat Disas Guangzhou Peoples R China;

    Sun Yat Sen Univ Sch Atmospher Sci Guangzhou Peoples R China|Sun Yat Sen Univ Guangdong Prov Key Lab Climate Change & Nat Disas Guangzhou Peoples R China;

    Sun Yat Sen Univ Sch Atmospher Sci Guangzhou Peoples R China|Sun Yat Sen Univ Guangdong Prov Key Lab Climate Change & Nat Disas Guangzhou Peoples R China;

    Univ Reading Sch Built Environm Reading Berks England;

    Hong Kong Univ Sci & Technol Dept Civil & Environm Engn Kowloon Clear Water Bay Hong Kong Peoples R China;

    Univ Hong Kong Dept Mech Engn Pok Fu Lam Rd Hong Kong Peoples R China;

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  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    Street canyon; Aspect ratio (AR); Wall heating; Street intake fraction lt; P_IF gt; Froude number; Computational fluid dynamic (CFD); simulations;

    机译：街峡谷;纵横比（AR）;壁加热;街道进气率_if;FRoude号码;计算流体动态（CFD）;模拟;

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