### 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 1 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

**A new semi-empirical model for estimating the drag coefficient of the vertical random staggered arrays using LES.** / Mohammad, Ahmad Faiz; Zaki, Sheikh Ahmad; Ikegaya, Naoki; Hagishima, Aya; Ali, Mohamed Sukri Mat.

Research output: Contribution to journal › Article

*Journal of Wind Engineering and Industrial Aerodynamics*, vol. 180, pp. 191-200. https://doi.org/10.1016/j.jweia.2018.08.003

}

TY - JOUR

T1 - A new semi-empirical model for estimating the drag coefficient of the vertical random staggered arrays using LES

AU - Mohammad, Ahmad Faiz

AU - Zaki, Sheikh Ahmad

AU - Ikegaya, Naoki

AU - Hagishima, Aya

AU - Ali, Mohamed Sukri Mat

PY - 2018/9/1

Y1 - 2018/9/1

N2 - 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, CD. The vertical random arrays are configured in several frontal area densities, λF (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, Cp(t) normalized with that of the isolated building, Cp(iso). The ratio Cp(t)/Cp(iso) is well correlated with the target building's frontal area density, λf(t). Subsequently, the relationship between Cp(t) and λf(t) is expressed using power law equations for three building categories based on the height-to-width ratio, αp(t): tall (2.64 ≤ αp(t) ≤ 3.76), medium-rise (1.32 ≤ αp(t) ≤ 2.00), and low-rise (0.36 ≤ αp(t) ≤ 0.84). Based on the Cp(t), an equation of the CD is formulated, yielding the following outcomes. Firstly, the predicted CD values are mostly within 10% of the previous experimental results. Secondly, a semi-empirical model is derived, whereby the predicted CD values are generally consistent for various vertical random arrays.

AB - 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, CD. The vertical random arrays are configured in several frontal area densities, λF (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, Cp(t) normalized with that of the isolated building, Cp(iso). The ratio Cp(t)/Cp(iso) is well correlated with the target building's frontal area density, λf(t). Subsequently, the relationship between Cp(t) and λf(t) is expressed using power law equations for three building categories based on the height-to-width ratio, αp(t): tall (2.64 ≤ αp(t) ≤ 3.76), medium-rise (1.32 ≤ αp(t) ≤ 2.00), and low-rise (0.36 ≤ αp(t) ≤ 0.84). Based on the Cp(t), an equation of the CD is formulated, yielding the following outcomes. Firstly, the predicted CD values are mostly within 10% of the previous experimental results. Secondly, a semi-empirical model is derived, whereby the predicted CD values are generally consistent for various vertical random arrays.

UR - http://www.scopus.com/inward/record.url?scp=85053070757&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85053070757&partnerID=8YFLogxK

U2 - 10.1016/j.jweia.2018.08.003

DO - 10.1016/j.jweia.2018.08.003

M3 - Article

AN - SCOPUS:85053070757

VL - 180

SP - 191

EP - 200

JO - Journal of Industrial Aerodynamics

JF - Journal of Industrial Aerodynamics

SN - 0167-6105

ER -