Pollutant dispersion and thermal effects in urban street canyons

Sini, J.-F.; Anquetin, Sandrine; Mestayer, P.G.

doi:10.1016/1352-2310(95)00321-5

Cited by 492 publications

(263 citation statements)

References 16 publications

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“…When the thermal effects are substantial (due to solar radiation, the release of stored heat, and anthropogenic heat for example) they can have a profound impact on the thermal field itself, the flow field and therefore the pollutant dispersion in street canyons, as demonstrated by many previous studies [44][45][46][47][48]. The main parameter characterizing the stability is the bulk Richardson number…”

Section: Flow and Dispersion Under Unstable/stable Stratificationsmentioning

confidence: 99%

Transport processes in and above two-dimensional urban street canyons under different stratification conditions: results from numerical simulation

Britter

Norford

2014

Environ Fluid Mech

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Thermal stratification (neutral, unstable and stable) plays an important role in determining the transport processes in and above urban street canyons. This paper summarizes the recent findings of the effect of thermal stratification on the transport of momentum, heat, and pollutants in the two-dimensional (2D) urban street canyons in the skimming flow regime. Special attention is paid to the results from large-eddy simulations (LESs), while other experimental and numerical results are referred to when necessary. With increasing Richardson number, Ri, the drag coefficient of the 2D street canyon as felt by the overlying atmosphere decreases in a linear manner. Under neutral and stable stratification, a nearly constant drag coefficient of 0.02 is predicted by the LESs. Under unstable stratification, the turbulent pollutant transport is dominated by organized turbulent motions (ejections and sweeps), while under stable stratification, the unorganized turbulent motion (inward interactions) plays a more important role and the sweeps are inhibited. The unstable stratification condition also enhances the ejections of turbulent pollutant flux, especially at the leeward roof-level corner, where the ejections dominate the turbulent pollutant flux, outweighing the sweeps. With increasing Ri, both the heat (area active scalar source) and pollutant (line passive scalar source) transfer coefficients decrease towards a state where the transfer coefficients become zero at Ri ≈ 0.5. It should be noted that, due to the limit of the 2D street canyon configuration discussed in this paper, great caution should be taken when generalising the conclusions drawn here.

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Section: Flow and Dispersion Under Unstable/stable Stratificationsmentioning

confidence: 99%

Transport processes in and above two-dimensional urban street canyons under different stratification conditions: results from numerical simulation

Britter

Norford

2014

Environ Fluid Mech

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“…The domain inflow and outflow length was set equal to 10 5H. This configuration was selected as this provides enough length in the upstream region to 11 develop the boundary layer (Sini et al, 1996). A similar domain was used by Solazzo and 12 Britter (2007a).…”

Section: Domainmentioning

confidence: 99%

Comparative study of measured and modelled number concentrations of nanoparticles in an urban street canyon

Kumar

Garmory

Ketzel³

et al. 2009

Atmospheric Environment

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“…The latter type studies turbulent airflows and pollutant dispersion on the microscale, i.e. around isolated buildings (Li and Stathopoulos 1997), in two-dimensional (2D) street canyons (Oke 1988;Sini et al 1996;Baik and Kim 2002;Liu et al 2005;Xie et al 2006;Li et al 2009), in groups of building arrays (Hanna et al 2002;Chang and Meroney 2003;Britter and Hanna 2003;Belcher 2005;Martilli and Santiago 2007;Santiago et al 2007Santiago et al , 2008) using large-eddy simulation (LES) or microscopic simulations with Reynoldsaveraged Navier-Stokes (RANS) turbulence models or wind-tunnel experiments. Cheng et al (2003) investigated the turbulent flow over a matrix of cubes with a LES model and a RANS standard k-ε model.…”

Section: Introductionmentioning

confidence: 99%

Wind Conditions in Idealized Building Clusters: Macroscopic Simulations Using a Porous Turbulence Model

Hang

2010

Boundary-Layer Meteorol

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Simulating turbulent flows in a city of many thousands of buildings using general high-resolution microscopic simulations requires a grid number that is beyond present computer resources. We thus regard a city as porous media and divide the whole hybrid domain into a porous city region and a clear fluid region, which are represented by a macroscopic k-ε model. Some microscopic information is neglected by the volume-averaging technique in the porous city to reduce the calculation load. A single domain approach is used to account for the interface conditions. We investigated the turbulent airflow through aligned cube arrays (with 7, 14 or 21 rows). The building height H, the street width W, and the building width B are the same (0.15 m), and the fraction of the volume occupied by fluid (i.e. the porosity) is 0.75; the approaching flow is parallel to the main streets. There are both microscopic and macroscopic simulations, with microscopic simulations being well validated by experimental data. We analysed microscopic wind conditions and the ventilation capacity in such cube arrays, and then calculated macroscopic time-averaged properties to provide a comparison for macroscopic simulations. We found that the macroscopic k-ε turbulence model predicted the macroscopic flow reduction through porous cube clusters relatively well, but under-predicted the macroscopic turbulent kinetic energy (TKE) near the windward edge of the porous region. For a sufficiently long porous cube array, macroscopic flow quantities maintain constant conditions in a fully developed region.

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Pollutant dispersion and thermal effects in urban street canyons

Cited by 492 publications

References 16 publications

Transport processes in and above two-dimensional urban street canyons under different stratification conditions: results from numerical simulation

Transport processes in and above two-dimensional urban street canyons under different stratification conditions: results from numerical simulation

Comparative study of measured and modelled number concentrations of nanoparticles in an urban street canyon

Wind Conditions in Idealized Building Clusters: Macroscopic Simulations Using a Porous Turbulence Model

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