Volumetric drag coefficients for generic urban configurations: Insights from canopy flow analysis

Mingjie Zhang, Oliver Carlo, Yunlong Peng, Zhi Gao, Jianshun Zhang, Guohua Ji, Riccardo Buccolieri

Research output: Contribution to journalArticlepeer-review

Abstract

Alternative drag approaches for representing unresolved buildings were proposed in literature for computational fluid dynamics (CFD) simulation of macroscopic urban airflow. As a contribution, the present work derives the volumetric drag coefficient (Cd*) through canopy drag and velocity analysis and provides appropriate correlations for Cd*against urban morphological parameters. A total of 72 cases across various urban configurations are investigated, categorized by building typology, horizontal layout, height variability, and plan area density (λp, from 0.0625 to 0.57). Reynolds-Averaged Navier-Stokes (RANS) simulations with periodic boundary conditions are performed to model fully developed flows. Results for the normalized drag force and superficial velocity and their relations with λp are evaluated. Subsequent evaluation of the profiles for the sectional coefficients (Cd*(Z)) reveals four distinct types with variations in uniform-height cases and combinations in varying-height cases. A throughout correlations analysis, facilitated by data transformation, identifies the straightforward relations between Cd* and frontal area density (λf) and tortuosity (τ). The followed stepwise regression provides a recommended formula for Cd*, demonstrating a proper fit with the simulated values. These findings facilitate the understanding and appropriate estimation of Cd* and Cd*(Z), promoting the application of macroscopic turbulence models, for neighborhood-scale wind and air quality studies.

Original languageEnglish (US)
Article number112273
JournalBuilding and Environment
Volume267
DOIs
StatePublished - Jan 1 2025

Keywords

  • Drag parameterization
  • Height variability
  • Simplified airflow model
  • Stepwise regression
  • Urban morphology
  • Urban ventilation

ASJC Scopus subject areas

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

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