### Abstract

Sheltering of buildings has a significant impact on the total drag of an urban surface. This study performs large eddy simulations (LESs) of flows over vertical random arrays (comprised of buildings with height variability) in staggered layout to estimate the drag coefficient, C_{D}. The vertical random arrays are configured in several frontal area densities, λ_{F} (ratio of buildings’ frontal area to total surface area) ranging from 0.09 to 0.81. The sheltering effect is parameterized using the individual building's wind pressure coefficient, C_{p(t)} normalized with that of the isolated building, C_{p(iso)}. The ratio C_{p(t)}/C_{p(iso)} is well correlated with the target building's frontal area density, λ_{f(t)}. Subsequently, the relationship between C_{p(t)} and λ_{f(t)} is expressed using power law equations for three building categories based on the height-to-width ratio, α_{p(t)}: tall (2.64 ≤ α_{p(t)} ≤ 3.76), medium-rise (1.32 ≤ α_{p(t)} ≤ 2.00), and low-rise (0.36 ≤ α_{p(t)} ≤ 0.84). Based on the C_{p(t)}, an equation of the C_{D} is formulated, yielding the following outcomes. Firstly, the predicted C_{D} values are mostly within 10% of the previous experimental results. Secondly, a semi-empirical model is derived, whereby the predicted C_{D} values are generally consistent for various vertical random arrays.

Original language | English |
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Pages (from-to) | 191-200 |

Number of pages | 10 |

Journal | Journal of Wind Engineering and Industrial Aerodynamics |

Volume | 180 |

DOIs | |

Publication status | Published - Sep 2018 |

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### All Science Journal Classification (ASJC) codes

- Civil and Structural Engineering
- Renewable Energy, Sustainability and the Environment
- Mechanical Engineering

### Cite this

*Journal of Wind Engineering and Industrial Aerodynamics*,

*180*, 191-200. https://doi.org/10.1016/j.jweia.2018.08.003