Large-Eddy Simulation Analyses of Heated Urban Canyon Facades

Carlo Cintolesi, Francesco Barbano and Silvana Di Sabatino
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Carlo Cintolesi: Department of Physics and Astronomy, University of Bologna, via Irnerio 46, 40126 Bologna, Italy
Francesco Barbano: Department of Physics and Astronomy, University of Bologna, via Irnerio 46, 40126 Bologna, Italy
Silvana Di Sabatino: Department of Physics and Astronomy, University of Bologna, via Irnerio 46, 40126 Bologna, Italy

Energies, 2021, vol. 14, issue 11, 1-22

Abstract: Thermal convective flows are common phenomena in real urban canyons and strongly affect the mechanisms of pollutant removal from the canyon. The present contribution aims at investigating the complex interaction between inertial and thermal forces within the canyon, including the impacts on turbulent features and pollutant removal mechanisms. Large-eddy simulations reproduce infinitely long square canyons having isothermal and differently heated facades. A scalar source on the street mimics the pollutant released by traffic. The presence of heated facades triggers convective flows which generate an interaction region around the canyon-ambient interface, characterised by highly energetic turbulent fluxes and an increase of momentum and mass exchange. The presence of this region of high mixing facilitates the pollutant removal across the interface and decreases the urban canopy drag. The heating-up of upwind facade determines favourable convection that strengthens the primary internal vortex and decreases the pollutant concentration of the whole canyon by 49 % compare to the isothermal case. The heating-up of the downwind facade produces adverse convection counteracting the wind-induced motion. Consequently, the primary vortex is less energetic and confined in the upper-canyon area, while a region of almost zero velocity and high pollution concentration ( 40 % more than the isothermal case) appears at the pedestrian level. Finally, numerical analyses allow a definition of a local Richardson number based on in-canyon quantities only and a new formulation is proposed to characterise the thermo-dynamics regimes.

Keywords: urban canyon; convective flows; pollutant removal; turbulence; large-eddy simulation (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
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