CFD simulations of wind flow and pollutant dispersion in a street canyon with traffic flow: Comparison between RANS and LES

This paper reports on the model sensitivity analysis of a commercial computational fluid dynamics program, ANSYS FLUENT v14. The purpose of the analysis was to determine the appropriate modeling settings for numerical model of the case study. A full scale of a simplified urban street canyon was modelled and the turbulent flow was calculated using Large Eddy Simulation (LES) techniques. The model sensitivity tests involved are mesh sensitivity, statistically steady state and sampling. Adequate numbers of cells, period time to achieve statistically steady state (SST) and sampling time to simulate wind flow and pollutant dispersion in street canyon were determined through systematic tests.

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Large-eddy simulations of wind flow and pollutant dispersion in a street canyon

Atmospheric Environment ◽

10.1016/j.atmosenv.2005.02.044 ◽

2005 ◽

Vol 39 (20) ◽

pp. 3573-3582 ◽

Cited By ~ 32

Author(s):

Ellen S.P. So ◽

Andy T.Y. Chan ◽

Anton Y.T. Wong

Keyword(s):

Street Canyon ◽

Pollutant Dispersion ◽

Large Eddy Simulations ◽

Wind Flow ◽

Large Eddy

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Numerical Simulation of Wind Flow Structures and Pollutant Dispersion within Street Canyon under Thermally Unstable Atmospheric Conditions

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.554.655 ◽

2014 ◽

Vol 554 ◽

pp. 655-659 ◽

Cited By ~ 2

Author(s):

Afiq Muhammad Yazid Witri ◽

Nor Azwadi Che Sidik ◽

Salim Mohamed Salim

Keyword(s):

Street Canyon ◽

Turbulence Models ◽

Pollutant Dispersion ◽

Heated Wall ◽

Flow Structures ◽

Wind Flow ◽

Atmospheric Conditions ◽

Buoyancy Flow ◽

Numerical Studies ◽

Vortex Intensification

Numerical studies were conducted to envisage the wind flow structures in street canyon for differential heated wall and Richardson numbers. Two-equation turbulence models, namely the Standard k-ε, Renormalization Group (RNG) k-ε and Realizable k-ε were applied to investigate the effect of flow structure on pollutant dispersion in a square street canyon. The obtained results demonstrate that the differentially heated wall/floor gives significant effects on the wind flow field compared with those under isothermal conditions. At low Richardson number, vortex intensification was observed for the case of ground or leeward heated wall. Meanwhile, for the case of windward heated wall, the ventilation was much reduced due to the buoyancy force that produces upward motion near the wall to form the secondary vortex. At higher Froude number (convective flows) case, the buoyancy flow has no discernible effects on the flow structures. Keywords— Street canyon; thermal flow; wind flow structures; pollutant dispersion; turbulence models

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