Dispersion of air pollutants around buildings: A review of past studies and their methodologies

Abstract

The review shows that on-site measurement has the benefit of obtaining real life data under real atmospheric boundary layer conditions, but it is too difficult to capture the real atmospheric conditions and too expensive to conduct such experiment as too many samplers and receptors are needed, particularly for investigating the air pollutant issues with regard to building arrays. This difficulty can be solved by physical-scale modelling, which can provide more controllable airflow boundary conditions, but accuracy is compromised by its inability to simulate real boundary layer turbulence conditions and buoyancy effects. Water channel is advantageous in buoyancy experiments but maintaining realistic viscosity and density properties of the medium could be challenging. Direct numerical simulation can provide accurate results; but it is impractical to simulate flows in large domains due to high computational requirements. Reynold-averaged Navier–Stokes numerical simulation is the most commonly used model for pollutant dispersion and infection control analysis but generally over-predicts surface concentrations at the leeward side of a building. Although large eddy simulation can over-predict the lateral pollutant concentration in the wake region of the building, flow unsteadiness and intermittency can be solved.

Review on urban vegetation and particle air pollution – Deposition and dispersion

“…A few reviews have been published in related areas, focussing on e.g. particle deposition on vegetation (Litschke and Kuttler, 2008); dry deposition on plant canopies (Petroff et al, 2008a); urban green space and social justice (Wolch et al, 2014); and dispersion without the complication of vegetation (Xia et al, 2014). Many studies have attempted to estimate the economic benefits of improving air quality, although the effect of vegetation on urban air quality is not yet fully understood (Tiwary et al, 2009;Escobedo et al, 2011).…”

On the use of numerical modelling for near-field pollutant dispersion in urban environments − A review

“…Meroney et al, 1975;Meroney and Hatcher, 1977;Meroney, 1982;H€ aggkvist et al, 1989;Rotach, 1993b;Johnson and Hunter, 1998;Roth, 2000;Cheng et al, 2003;Lien et al, 2004;Calhoun et al, 2005;Ricciardelli and Polimeno, 2006; Van- 3 The term "physical modelling" refers to the reduced-scale measurements that are commonly conducted for studying airflow and pollutant dispersion around buildings (i.e. wind-tunnel and/or water-channel experiments) as specified by Xia et al (2014). Therefore, this note will remain valid for the rest of this work.…”

“…However, when modelling a neutral atmospheric boundary layer for outdoor environmental applications (e.g. pedestrian wind environment around buildings, wind-driven rain on building facades and air pollutant dispersion around buildings), the mean velocity profile is expressed either by a logarithmic law or a power law Xia et al, 2014).…”

“…Field measurements mean that the flow and concentration tests are conducted under real atmospheric conditions (Xia et al, 2014). However, full-scale measurements are usually performed on a limited number of points in space (Montazeri and Blocken, 2013).…”

CFD investigation on the effects of wind and thermal wall-flow on pollutant transmission in a high-rise building

“…Such long-distance routes of transmission are called airborne transmission, which is reported to be one of the major respiratory syndrome transmission routes by numerous engineering and epidemiological studies [2][3][4][5]. A lot of researches involving airflow patterns and aerosol-transmitted scenarios in multiscale area have been done by onsite full-scale measurements, reduced-scale wind/water tunnel experiments and computational fluid dynamics (CFD) techniques [6][7][8][9]. For urban scale, the airflow is complicated because of the interaction with the inhomogeneous underlying surfaces [8].…”