The effects of thermal stratification on airborne transport within the urban roughness sublayer

doi:10.1016/j.ijheatmasstransfer.2021.122289

	The effects of thermal stratification on airborne transport within the urban roughness sublayer
	Cai, Junjie 1; Chen, Jingtan 1; Cheng, Haimei 2; Zi, Shuangfei 2; Xiao, Jinchao 2; Xia, Fan 1,3,4; Zhao, Jiyun 1
刊名	INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
	2022-03-01
卷号	184
关键词	Thermal stratification Atmospheric dispersion Urban roughness sublayer (RSL) Computational fluid dynamics (CFD) Scalar fluxes Transfer coefficients
ISSN号	0017-9310
DOI	10.1016/j.ijheatmasstransfer.2021.122289
通讯作者	Zhao, Jiyun(jiyuzhao@cityu.edu.hk)
英文摘要	The release of airborne hazardous substances in the urban roughness sublayer (RSL) is a risk to human health. The atmospheric dispersion of these materials should be contained to mitigate their adverse consequences. This study investigates the effects of atmospheric stability on the air, heat, and pollutant transport within RSL by a validated 3-D RANS code. A building morphology with height variance is proposed for better representing the real urban environment and characterizing the complex interactions between the roughness elements and the flow regimes. The thermal stratification stability test subject to the ground-inflow temperature difference is extended to span from strongly unstable to moderately stable. The quantitative indicators, including air exchange rate, heat removal rate, pollutant removal rate, heat transfer coefficient, and pollutant transfer coefficient, are introduced and analyzed. The correlations between indicators and thermal stabilities are established, which provides explicit expressions to describe the influence of the changing bulk Richardson number (Rb). Results show that the design of height variance elements enables a stronger lateral momentum towards the target street canyon, which suppresses the spanwise dispersion of pollutants. The discussions upon heat and pollutant transport based on stability categories show a high Rb-dependence of heat/mass transfer efficiency. The stability threshold is demonstrated to be Rb approximate to 0.7, where the flow speed near the ground approaches zero. As a result, the high temperature gradient is formed and acts as positive feedback to facilitate a more stratified condition. The accurate and rational correlations obtained in this study will save the computational cost considerably for further research. Also, the available results will be a reference for environmentally friendly designs. (c) 2021 Elsevier Ltd. All rights reserved.
资助项目	Guangzhou Science & Technology and Innovation Commission[201907010007]
WOS关键词	FIELD POLLUTANT DISPERSION ; LARGE-EDDY SIMULATION ; WIND-TUNNEL MEASUREMENTS ; STREET CANYONS ; TURBULENT-FLOW ; NUMERICAL INVESTIGATIONS ; ATMOSPHERIC DISPERSION ; CITY BREATHABILITY ; CFD SIMULATIONS ; RE-INDEPENDENCE
WOS研究方向	Thermodynamics ; Engineering ; Mechanics
语种	英语
出版者	PERGAMON-ELSEVIER SCIENCE LTD
WOS记录号	WOS:000755378200002
资助机构	Guangzhou Science & Technology and Innovation Commission
内容类型	期刊论文
源URL	[http://ir.hfcas.ac.cn:8080/handle/334002/127772]
专题	中国科学院合肥物质科学研究院
通讯作者	Zhao, Jiyun
作者单位	1.City Univ Hong Kong, Dept Mech Engn, Hong Kong, Peoples R China 2.Chinese Acad Sci, Shenyang Inst Automat Guangzhou, Guangzhou 511458, Peoples R China 3.Chinese Acad Sci, Inst Nucl Energy Safety Technol, Hefei Inst Phys Sci, Key Lab Neutron & Radiat Safety, Hefei 230031, Peoples R China 4.Univ Sci & Technol China, Hefei 230026, Peoples R China
推荐引用方式 GB/T 7714	Cai, Junjie,Chen, Jingtan,Cheng, Haimei,et al. The effects of thermal stratification on airborne transport within the urban roughness sublayer[J]. INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER,2022,184.
APA	Cai, Junjie.,Chen, Jingtan.,Cheng, Haimei.,Zi, Shuangfei.,Xiao, Jinchao.,...&Zhao, Jiyun.(2022).The effects of thermal stratification on airborne transport within the urban roughness sublayer.INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER,184.
MLA	Cai, Junjie,et al."The effects of thermal stratification on airborne transport within the urban roughness sublayer".INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER 184(2022).