Towards the application of indoor ventilation efficiency indices to evaluate the air quality of urban areas

Bady, Mahmoud; Kato, Shinsuke; Huang, Hong

doi:10.1016/j.buildenv.2007.11.013

Cited by 125 publications

(65 citation statements)

References 19 publications

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“…At inlet boundary, the constant flux layer assumption was adopted to generate a turbulent energy 'k' and dissipation rate 'ε'. The inflow wind speed was set to obey the one-fourth power law relationship and the inlet turbulence intensity was assumed to be 10% of the reference wind speed (Bady et al, 2008).…”

Section: Cfd Simulations Approachmentioning

confidence: 99%

Evaluation of Gaussian Plume Model against CFD Simulations through the Estimation of CO and NO Concentrations in an Urban Area

Bady

2017

American Journal of Environmental Sciences

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Dispersion of air pollutants, Carbon monoxide (CO) and Nitrogen oxide (NO), due to three point sources and a high-density traffic road in an urban area located near the center of Tokyo, Japan was studied using two different approaches. The first is an analytical approach using Gaussian Plume Model (GPM) while the second is a numerical approach using Computational Fluid Dynamics (CFD) simulations. In the first approach, the study area was divided into a fine grid and the traffic road was treated as a number of continuous adjacent stacks. The GPM was applied upon each stack and the concentration at each receptor was calculated using the principle of superposition. CFD simulations were carried out where steady state analysis was adopted and the standard k-ε turbulence model was used. The concentrations calculated with the two approaches were compared together. The study results show that the agreement between the concentrations estimated by the two approaches was good in low-density built-up locations within the study area while significant deviation was obtained for high-density locations. Such result reflects the fact that the GPM is poor in predicting the actual concentrations in cases of densely urban areas.

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Section: Cfd Simulations Approachmentioning

confidence: 99%

Evaluation of Gaussian Plume Model against CFD Simulations through the Estimation of CO and NO Concentrations in an Urban Area

Bady

2017

American Journal of Environmental Sciences

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“…The importance of such investigations is associated with the increased levels of air pollutants in the atmosphere around urban areas. This increase has various causes, such as the continuing expansion of existing industries and the increased use of motor vehicles coupled with population growth, particularly in large urban areas (Bady et al, 2008). People who breathe in air pollutants, such as ozone, nitrogen oxides, or particulate matter (PM), may suffer from respiratory disease and even lung cancer (WHO, 2000).…”

Section: Introductionmentioning

confidence: 99%

Evaluating Dust Particle Transport Performance within Urban Street Canyons with Different Building Heights

Mercola

Deng

et al. 2016

Aerosol Air Qual. Res.

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In developing cities, buildings with different heights obstruct the diffusion of pollutants. In this study, dust particles transported within urban street canyons were simulated using Reynolds-averaged Navier-Stokes (RANS) method, and airsolid two-phase flow fields were obtained on a regional scale. Four typical street building models were used in this study: (a) low-rise buildings (H/b = 1), (b) step-up building arrangements (H/b = 1, 2, 3, 4, 5), (c) step-down building arrangement (H/b = 5, 4, 3, 2, 1), and (d) high-rise buildings (H/b = 5). The particle volume fraction distribution in the four models reflected the basic properties of particle transportation in the canyons. Vortices were observed on the roofs of street canyons, which prevented particles from being transmitted into the canyons, and the vortex regions were characterized as low particle concentration.To evaluate the dust particle transport performance in the models, three indices, namely particle transport efficiency, suspension fraction and suspension density, were defined. These concepts were based on the particle number concentrations, which were obtained using the Lagrange approach. The high-rise building model (H/b = 5) demonstrated the lowest transport efficiency among all four models, and it also had the lowest suspension density in the street canyons. This implied that the high-rise buildings hindered the particles from being transporting further and that the particles could not enter the deep canyons easily. In the step-down building arrangement model (H/b = 5, 4, 3, 2, 1), the particle concentration level and suspension density in the canyons were lower than those observed in the step-up building arrangement model (H/b = 1, 2, 3, 4, 5), indicating that a step-down building height arrangement is appropriate for creating construction plans for developing cities.Finally, the variation of the streamwise air velocity, vertical velocity and fluctuating velocity on the roof of canyons along the x direction were separately examined. Notably, the fluctuating velocity was the dominant mechanism of the particle suspension in the canyons.

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“…In that study, three VE indices-purging flow rate (PFR: the effective airflow rate required to purge pollutants from the domain), visitation frequency (VF: the number of times a pollutant enters the domain and passes through it) and air residence time (TP: the time elapsed between when a pollutant enters or is generated in the domain until it exits)-introduced by Bady et al were adopted by performing calculations using the CFD method. However, the results showed that PFR and TP depend greatly on space volume, as Bady et al noted [13]. These indices were limited to analyzing the effect of design variations on regional spatial ventilation.…”

Section: Introductionmentioning

confidence: 99%

“…For example, Bady et al [13] and Kato and Huang [14] introduced some indoor ventilation parameters and developed a series of scales concept for evaluating VE in urban spaces. Through evaluation of several examples, the studies showed that these ventilation indices appear to be a promising tool for urban ventilation study.…”

Section: Assessment Of Urban Spatial Ventilationmentioning

confidence: 99%

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Improving Residential Wind Environments by Understanding the Relationship between Building Arrangements and Outdoor Regional Ventilation

et al. 2017

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This paper explores the method of assessing regional spatial ventilation performance for the design of residential building arrangements at an operational level. Three ventilation efficiency (VE) indices, Net Escape Velocity (NEV), Visitation Frequency (VF) and spatial-mean Velocity Magnitude (VM), are adopted to quantify the influence of design variation on VE within different regional spaces. Computational Fluid Dynamics (CFD) method is applied to calculate VE indices mentioned above. Several residential building arrangement cases are set to discuss the effect of different building length, lateral spacing and layouts on four typical space patterns under wind directions oblique or perpendicular to the main (long) building facade. The simulation results prove that NEV, VF and VM are useful VE indices, which can reflect different features of flow pattern in studied regional domains. Preliminary parametric studies indicate that wind direction might be the most important factor for improving spatial ventilation. When the angle between main building facade and wind direction is more than 30 • , ventilation of different exterior spaces could improve evidently. When wind direction is perpendicular to main building façade, decreasing building length can increase NEV of the middle space by 50%, while decreasing lateral spacing would decrease NEV of the intersection space by 35%.

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Towards the application of indoor ventilation efficiency indices to evaluate the air quality of urban areas

Cited by 125 publications

References 19 publications

Evaluation of Gaussian Plume Model against CFD Simulations through the Estimation of CO and NO Concentrations in an Urban Area

Evaluation of Gaussian Plume Model against CFD Simulations through the Estimation of CO and NO Concentrations in an Urban Area

Evaluating Dust Particle Transport Performance within Urban Street Canyons with Different Building Heights

Improving Residential Wind Environments by Understanding the Relationship between Building Arrangements and Outdoor Regional Ventilation

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