TY - JOUR
T1 - Numerical simulations on atmospheric stability conditions and urban airflow at five climate zones in China
AU - Chen, Guoxing
AU - Rong, Li
AU - Zhang, Guoqiang
PY - 2021/4
Y1 - 2021/4
N2 - Due to the quick development of urbanization, it is important to provide a healthy urban environment for the dweller. Previous studies have obtained valuable conclusions of how to improve the urban airflow distribution under isothermal conditions. How to adopt and interpret those conclusions when considering the solar-induced atmospheric stability conditions have not been clarified yet. In this study, the characteristics of atmospheric stability condition and influence of diurnal varying solar-induced thermal effect on urban airflow inside the idealized building arrays were investigated at five cities located at five climate zones in China. Urban energy model, CitySim, was employed to simulate the annual distribution of solar-induced walls’ temperatures inside the idealized building arrays. The diurnal varying wall temperatures at the hottest days were set as thermal boundary conditions in computational fluid dynamic (CFD) simulations. With albedo value of 0.5, the possibility of adopting the results from isothermal condition directly ranged from 7% to 11% for the five cities in China throughout the year. The unstable condition ocuppied from 19% to 24% annually and the stable condition of more than 40% annually was observed. Under the diurnal varying solar-induced thermal effect, the spatially-averaged air speeds and airflow patterns were significantly different from the isothermal conditions. The percent of Richardson number under different atmospheric stability conditions annually based on the Citysim simulation results indicated that the atmospheric stability was most likely determined by the local climate characteristics and albedo value rather than the building layouts at the five selected cities in China, but this should be further investigated when the shadow effects of surrounding buildings were considered in simulations.
AB - Due to the quick development of urbanization, it is important to provide a healthy urban environment for the dweller. Previous studies have obtained valuable conclusions of how to improve the urban airflow distribution under isothermal conditions. How to adopt and interpret those conclusions when considering the solar-induced atmospheric stability conditions have not been clarified yet. In this study, the characteristics of atmospheric stability condition and influence of diurnal varying solar-induced thermal effect on urban airflow inside the idealized building arrays were investigated at five cities located at five climate zones in China. Urban energy model, CitySim, was employed to simulate the annual distribution of solar-induced walls’ temperatures inside the idealized building arrays. The diurnal varying wall temperatures at the hottest days were set as thermal boundary conditions in computational fluid dynamic (CFD) simulations. With albedo value of 0.5, the possibility of adopting the results from isothermal condition directly ranged from 7% to 11% for the five cities in China throughout the year. The unstable condition ocuppied from 19% to 24% annually and the stable condition of more than 40% annually was observed. Under the diurnal varying solar-induced thermal effect, the spatially-averaged air speeds and airflow patterns were significantly different from the isothermal conditions. The percent of Richardson number under different atmospheric stability conditions annually based on the Citysim simulation results indicated that the atmospheric stability was most likely determined by the local climate characteristics and albedo value rather than the building layouts at the five selected cities in China, but this should be further investigated when the shadow effects of surrounding buildings were considered in simulations.
KW - Atmospheric stability
KW - CFD
KW - CitySim
KW - Solar-induced thermal boundary conditions
KW - Urban airflow
UR - http://www.scopus.com/inward/record.url?scp=85111337046&partnerID=8YFLogxK
U2 - 10.1016/j.enbenv.2020.07.006
DO - 10.1016/j.enbenv.2020.07.006
M3 - Journal article
SN - 2666-1233
VL - 2
SP - 188
EP - 203
JO - Energy and Built Environment
JF - Energy and Built Environment
IS - 2
ER -