Reduced-scale numerical investigation of airflow around low-medium density neighbourhoods from the perspectives of drag force and ventilation efficiency

Mingjie Zhang, Jiaying Li, Olga Palusci, Zhi Gao, Guohua Ji, Jianshun Zhang, Riccardo Buccolieri

Research output: Contribution to journalArticlepeer-review

Abstract

Relevant drag measurements in wind tunnels contributed to the drag parametrization. This reduced-scale numerical work further examines drag distribution and the relation between drag force and outdoor ventilation efficiency. Neighbourhood-like block arrays with planar area densities (λp) from 0.0625 to 0.25 and five distinct form types are investigated, extending a prior drag experiment solely on cube regular arrays. The approaching flow reshaped by these arrays exhibits flow adjustment and drag evolution. Drag distribution analysis demonstrates varied shelter effects and different shapes of sectional drag profiles. Arrays featuring larger λp and staggered layout generally exhibit higher normalized bulk drag force (Fbulk), but lower normalized frontal area-averaged drag (FAf,ave). Further, Fbulk and FAf,ave demonstrate strong negative correlations with normalized spatially averaged velocity, showing the potential to reflect the ventilation efficiency within neighbourhoods. Drag area density and drag-to-frontal area ratio are assessed as alternatives to interpret the drag, and it reveals half of the physical frontal area for medium arrays can serve as approximately estimated drag area. It is noted that the qualitative evaluation provides insights into the drag distribution and drag interpretation, while the quantitative correlation is limited to the examined morphological scenarios.

Original languageEnglish (US)
Article number102158
JournalUrban Climate
Volume58
DOIs
StatePublished - Nov 2024

Keywords

  • Aerodynamic drag
  • City breathability
  • Drag area
  • Drag interpretation
  • Planar area density
  • Urban morphology

ASJC Scopus subject areas

  • Geography, Planning and Development
  • Environmental Science (miscellaneous)
  • Urban Studies
  • Atmospheric Science

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