Large-Eddy Simulation of Flow and Pollutant Transport in Urban Street Canyons with Ground Heating |
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| Authors: | Xian-Xiang Li Rex E Britter Tieh Yong Koh Leslie K Norford Chun-Ho Liu Dara Entekhabi Dennis Y C Leung |
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| Institution: | (1) Laboratory of Heat Transfer and Environmental Engineering, Aristotle University, P.O. Box 483, 54124 Thessaloniki, Greece;(2) NCSR “Demokritos”, Institute of Nuclear Technology—Radiation Protection, Environmental Research Laboratory, Athens, Greece |
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| Abstract: | Our study employed large-eddy simulation (LES) based on a one-equation subgrid-scale model to investigate the flow field and
pollutant dispersion characteristics inside urban street canyons. Unstable thermal stratification was produced by heating
the ground of the street canyon. Using the Boussinesq approximation, thermal buoyancy forces were taken into account in both
the Navier–Stokes equations and the transport equation for subgrid-scale turbulent kinetic energy (TKE). The LESs were validated
against experimental data obtained in wind-tunnel studies before the model was applied to study the detailed turbulence, temperature,
and pollutant dispersion characteristics in the street canyon of aspect ratio 1. The effects of different Richardson numbers
(Ri) were investigated. The ground heating significantly enhanced mean flow, turbulence, and pollutant flux inside the street
canyon, but weakened the shear at the roof level. The mean flow was observed to be no longer isolated from the free stream
and fresh air could be entrained into the street canyon at the roof-level leeward corner. Weighed against higher temperature,
the ground heating facilitated pollutant removal from the street canyon. |
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