TY - JOUR
T1 - Modelling chemistry and transport in urban street canyons
T2 - comparing offline multi-box models with large-eddy simulation
AU - Dai, Yuqing
AU - Cai, Xiaoming
AU - Zhong, Jian
AU - MacKenzie, A. Robert
PY - 2021/9/4
Y1 - 2021/9/4
N2 - Computational fluid dynamics models are resource-intensive, particularly when complex chemical schemes are implemented, and this computational expense limits their use in sensitivity analyses. We propose a flexible multi-box model that permits spatial disaggregation of sources and depositions to simulate the transportation and distribution of chemical species in street canyons with any aspect ratios for which a large eddy simulation (LES) of the flow exists. The spatial patterns of reactive species in the multi-box simulations are in good agreement with those from the LES, especially for the deep canyon from which air escapes more slowly. The overestimation of the LES simulation worsens somewhat due to segregations when the chemistry of volatile organic compounds (VOCs) is included but the overall pattern is captured in a modelling framework. By reducing computational costs by several orders of magnitude, the multi-box model allows more sensitivity testing than the LES, and is an effective approach to investigate spatial pattern of fast non-linear chemistry or microphysics at the street scale.
AB - Computational fluid dynamics models are resource-intensive, particularly when complex chemical schemes are implemented, and this computational expense limits their use in sensitivity analyses. We propose a flexible multi-box model that permits spatial disaggregation of sources and depositions to simulate the transportation and distribution of chemical species in street canyons with any aspect ratios for which a large eddy simulation (LES) of the flow exists. The spatial patterns of reactive species in the multi-box simulations are in good agreement with those from the LES, especially for the deep canyon from which air escapes more slowly. The overestimation of the LES simulation worsens somewhat due to segregations when the chemistry of volatile organic compounds (VOCs) is included but the overall pattern is captured in a modelling framework. By reducing computational costs by several orders of magnitude, the multi-box model allows more sensitivity testing than the LES, and is an effective approach to investigate spatial pattern of fast non-linear chemistry or microphysics at the street scale.
KW - Air quality
KW - Box models
KW - Nitrogen dioxide
KW - Ozone
KW - Street canyon
KW - Urban air pollution
UR - http://www.scopus.com/inward/record.url?scp=85114701815&partnerID=8YFLogxK
U2 - 10.1016/j.atmosenv.2021.118709
DO - 10.1016/j.atmosenv.2021.118709
M3 - Article
SN - 1352-2310
VL - 264
JO - Atmospheric Environment
JF - Atmospheric Environment
M1 - 118709
ER -