CFD modeling of pollution dispersion in a street canyon: Comparison between LES and RANS

Tominaga, Yoshihide; Stathopoulos, T.

doi:10.1016/j.jweia.2010.12.005

Cited by 258 publications

(106 citation statements)

References 38 publications

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“…It seems that no consensus exists in the literature on any particular value, considering the various values that can be found, e.g. 0.5 in [54], 0.6 in [55], 0.72 in [56] or 0.9 in [57].…”

Section: Mass Fluxesmentioning

confidence: 99%

Near-field pollutant dispersion in an actual urban area: Analysis of the mass transport mechanism by high-resolution Large Eddy Simulations

et al. 2015

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Graphical abstractHighlights -Pollutant dispersion in downtown Montreal is studied with high-resolution LES.-The contribution of the sub-grid scales to turbulent mass transport is minor in this case.-The results of this applied case are linked to those obtained for a generic isolated building.-The counter gradient mechanism of turbulent mass transport is observed.-With RANS, the turbulent flux model used should be able to reproduce this mechanism. AbstractLarge-Eddy Simulation of near-field pollutant dispersion from stacks on the roof of a low-rise building in downtown Montreal is performed. Two wind directions are considered, with different wind-flow patterns and plume behavior. The computed mean concentration field is analyzed by means of the convective and turbulent (including subgrid-scale) mass fluxes. This decomposition provides insight into the dispersion process and allows an evaluation of common turbulent transport models used with the Reynolds-Averaged Navier-Stokes approach, such as the standard gradient-diffusion hypothesis. Despite the specific character of the flow and dispersion patterns due to the complex geometry of the urban area under study, some similarities are found with the generic case of dispersion around an isolated simple building. Moreover, the analysis of dispersion in downtown Montreal is facilitated by the physical insight gained by the study of the generic case. In this sense, the present study supports the use of generic, simplified cases to investigate and understand environmental processes as they occur in real and more complex situations. Reciprocally, the results of this applied study show the influence on the dispersion process of the rooftop structures and of the orientation of the emitting building with respect to the incoming wind flow, providing directions for further research on generic cases.

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“…It seems that no consensus exists in the literature on any particular value, considering the various values that can be found, e.g. 0.5 in [54], 0.6 in [55], 0.72 in [56] or 0.9 in [57].…”

Section: Mass Fluxesmentioning

confidence: 99%

Near-field pollutant dispersion in an actual urban area: Analysis of the mass transport mechanism by high-resolution Large Eddy Simulations

et al. 2015

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“…The LES is used instead of the Reynoldsaveraged Navier-Stokes turbulence models because of its accuracy (Tominaga and Stathopoulos, 2011). The resolvedscale Navier-Stokes equations are…”

Section: Methodsmentioning

confidence: 99%

Large-eddy simulation of pollutant dispersion from a ground-level area source over urban street canyons with irreversible chemical reactions

Liu

Zhao

2014

Adv. Sci. Res.

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Abstract. In this study, the dispersion of chemically reactive pollutants is calculated by large-eddy simulation (LES) in a neutrally stratified urban canopy layer (UCL) over urban areas. As a pilot attempt, idealized street canyons of unity building-height-to-street-width (aspect) ratio are used. Nitric oxide (NO) is emitted from the ground surface of the first street canyon into the domain doped with ozone (O 3 ). In the absence of ultraviolet radiation, this irreversible chemistry produces nitrogen dioxide (NO 2 ), developing a reactive plume over the rough urban surface. A range of timescales of turbulence and chemistry are utilized to examine the mechanism of turbulent mixing and chemical reactions in the UCL. The Damköhler number (Da) and the reaction rate (r) are analyzed along the vertical direction on the plane normal to the prevailing flow at 10 m after the source. The maximum reaction rate peaks at an elevation where Damköhler number Da is equal or close to unity. Hence, comparable timescales of turbulence and reaction could enhance the chemical reactions in the plume.

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“…However, LES technique is very computationally demanding (Walton and Cheng, 2002). In addition, even though the LES technique is able to provide information about instantaneous fluctuations of concentration field, which cannot be obtained by RANS computations, more detailed investigations are required for its application in street canyons (Tominaga and Stathopoulos, 2011). In this paper, the RANS approach and the one equation Spalart-Allmaras (SA) turbulence model (Spalart and Allmaras, 1992) are employed.…”

Section: Numerical Modelling Of Ufps Distribution Inside Street Canyonsmentioning

confidence: 99%

Numerical Simulation of Ultrafine Particle Dispersion in Urban Street Canyons with the Spalart-Allmaras Turbulence Model

Scungio

Arpino

Stabile

et al. 2013

Aerosol Air Qual. Res.

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The increased traffic emissions and reduced ventilation of urban street canyons lead to the formation of high particle concentrations as a function of the related flow field and geometry. In this context, the use of advanced modelling tools, able to evaluate particle concentration under different traffic and meteorological conditions, may be helpful.In this work, a numerical scheme based on the non-commercial fully explicit AC-CBS algorithm, and the one-equation Spalart-Allmaras turbulence model, was developed to perform numerical simulations of fluid flow and ultrafine particle dispersion in different street canyon configurations and under different wind speed and traffic conditions. The proposed non-commercial numerical tool was validated through a comparison with data drawn from the scientific literature.The results obtained from ultrafine particle concentration simulations show that as the building height increases the dispersion of particles in the canyon becomes weaker, due to the restricted interaction between the flow field in the street canyon and the undisturbed flow. Higher values of approaching wind speed facilitate the dispersion of the particles. The traffic effect has been evaluated by imposing different values of particles emission, depending on the vehicles type, with the lowest concentration values obtained for the Euro 6 vehicles, and the highest for High Duty Vehicles. A parametric analysis was also performed concerning the exposure to particles of pedestrians in different positions at the road level as a function of street canyon geometry, traffic mode, and wind speed. The worst exposure (1.25 × 10 6 part./cm 3 ) was found at the leeward side for an aspect ratio H/W = 1, wind speed of 5 m/s when High Duty Vehicles traffic was considered.

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CFD modeling of pollution dispersion in a street canyon: Comparison between LES and RANS

Cited by 258 publications

References 38 publications

Near-field pollutant dispersion in an actual urban area: Analysis of the mass transport mechanism by high-resolution Large Eddy Simulations

Near-field pollutant dispersion in an actual urban area: Analysis of the mass transport mechanism by high-resolution Large Eddy Simulations

Large-eddy simulation of pollutant dispersion from a ground-level area source over urban street canyons with irreversible chemical reactions

Numerical Simulation of Ultrafine Particle Dispersion in Urban Street Canyons with the Spalart-Allmaras Turbulence Model

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