TY - JOUR
T1 - Impacts of building-height variability on turbulent coherent structures and pollutant dispersion
T2 - Large-eddy simulations
AU - Kim, Jong Won
AU - Baik, Jong Jin
AU - Park, Seung Bu
AU - Han, Beom Soon
N1 - Publisher Copyright:
© 2023 Turkish National Committee for Air Pollution Research and Control
PY - 2023/5
Y1 - 2023/5
N2 - In built-up urban areas, there are numerous buildings of various shapes and heights, and their collective impacts on urban flow and air quality are of great concern. Here, we numerically examine the impacts of building-height variability on turbulent coherent structures above an array of square buildings and pollutant dispersion using a large-eddy simulation model. Three simulations are conducted: no building-height variability case (σ/H = 0, where σ is the standard deviation of building heights and H is the average building height), small building-height variability case (σ/H = 0.25), and large building-height variability case (σ/H = 0.5). In the latter two cases, buildings of two different heights are alternately arranged. Pollutants are released from street level. As the building-height variability increases, the average pedestrian-level pollutant concentration decreases and its spatial variability becomes large. The building-height variability greatly influences turbulence intensity and vertical turbulent momentum and pollutant fluxes. The streamwise-elongated low- and high-speed flow structures appear in all three cases, and they are wider in the spanwise direction when there is building-height variability. Strong turbulent fluctuations seem to affect the spanwise extension of the high- and low-speed flow structures. Quadrant analysis shows that stronger ejection and sweep events are more frequent with increasing building-height variability. The regions of ejection (sweep) well coincide with those of pollutant ejection (pollutant sweep). When there is building-height variability, the streaky structures that appear also in the fields of instantaneous vertical turbulent momentum flux are somewhat wider in the spanwise direction.
AB - In built-up urban areas, there are numerous buildings of various shapes and heights, and their collective impacts on urban flow and air quality are of great concern. Here, we numerically examine the impacts of building-height variability on turbulent coherent structures above an array of square buildings and pollutant dispersion using a large-eddy simulation model. Three simulations are conducted: no building-height variability case (σ/H = 0, where σ is the standard deviation of building heights and H is the average building height), small building-height variability case (σ/H = 0.25), and large building-height variability case (σ/H = 0.5). In the latter two cases, buildings of two different heights are alternately arranged. Pollutants are released from street level. As the building-height variability increases, the average pedestrian-level pollutant concentration decreases and its spatial variability becomes large. The building-height variability greatly influences turbulence intensity and vertical turbulent momentum and pollutant fluxes. The streamwise-elongated low- and high-speed flow structures appear in all three cases, and they are wider in the spanwise direction when there is building-height variability. Strong turbulent fluctuations seem to affect the spanwise extension of the high- and low-speed flow structures. Quadrant analysis shows that stronger ejection and sweep events are more frequent with increasing building-height variability. The regions of ejection (sweep) well coincide with those of pollutant ejection (pollutant sweep). When there is building-height variability, the streaky structures that appear also in the fields of instantaneous vertical turbulent momentum flux are somewhat wider in the spanwise direction.
KW - Air quality
KW - Building-height variability
KW - Large-eddy simulation
KW - Pollutant dispersion
KW - Turbulent coherent structure
UR - http://www.scopus.com/inward/record.url?scp=85151240678&partnerID=8YFLogxK
U2 - 10.1016/j.apr.2023.101736
DO - 10.1016/j.apr.2023.101736
M3 - Article
AN - SCOPUS:85151240678
SN - 1309-1042
VL - 14
JO - Atmospheric Pollution Research
JF - Atmospheric Pollution Research
IS - 5
M1 - 101736
ER -