Effect of uneven building layout on air flow and pollutant dispersion in non-uniform street canyons

Zhao Lin Gu, Yun Wei Zhang, Yan Cheng, Shuncheng Lee

Research output: Journal article publicationJournal articleAcademic researchpeer-review

121 Citations (Scopus)

Abstract

Uneven building layouts and non-uniform street canyons are common in actual urban morphology. To study the effects of building layouts on air flow in non-uniform street canyons, various building arrangements are designed in this study. Simulations are carried out under four cases (i.e., a uniform street canyon as Case 1 and three non-uniform canyons as Cases 2-4) with parameter change of the occupying ratio of high buildings (ORHB) in the computational domain and their bilateral allocation as well as the combinations of stepup and/or stepdown notches. In the three non-uniform canyons, stepup and stepdown notches are separating (with ORHB of 25% for Case 2 and 75% for Case 4) or adjoining (with ORHB of 50% for Case 3). The air flow and pollutant dispersion in these street canyons are investigated using Large-eddy Simulation (LES). The air flow structures in the non-uniform street canyons are more complicated than in the uniform street canyon. Inside the non-uniform street canyons, the tilting, horizontal divergence and convergence of wind streamlines are found. Large-scale air exchanges of air mass inside and above the street canyons are found as well. At the pedestrian level, the concentrations of simulated pollutants (e.g., the mean and maximum concentrations) in the non-uniform street canyons are lower than those in the uniform one, suggesting that uneven building layouts are capable of improving the dispersion of pollutants in urban area. Further studies on Case 2-4 show that the separation of stepup and stepdown notches along the street increases the wind velocities in the vicinity of high buildings, while the adjoining of stepup and stepdown notches decreases the wind velocities. Low concentrations of pollutant at the pedestrian level are found in Case 2 compared to Cases 3 and 4. Thus, the separation of stepup and stepdown notches in non-uniform street canyons might be a good choice for uneven building layout arrangements from the point of view of pollutant dispersion and human health.
Original languageEnglish
Pages (from-to)2657-2665
Number of pages9
JournalBuilding and Environment
Volume46
Issue number12
DOIs
Publication statusPublished - 1 Dec 2011

Keywords

  • Air flow
  • LES
  • Non-uniform street canyon
  • Pollutant dispersion
  • Uneven building layout

ASJC Scopus subject areas

  • Environmental Engineering
  • Civil and Structural Engineering
  • Geography, Planning and Development
  • Building and Construction

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