Large-Eddy Simulation Analyses of Heated Urban Canyon Facades
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 turbulen...
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| Format: | Article |
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MDPI AG
2021-05-01
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| Series: | Energies |
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| Online Access: | https://www.mdpi.com/1996-1073/14/11/3078 |
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| author | Carlo Cintolesi Francesco Barbano Silvana Di Sabatino |
| author_facet | Carlo Cintolesi Francesco Barbano Silvana Di Sabatino |
| author_sort | Carlo Cintolesi |
| collection | DOAJ |
| description | 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 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>49</mn><mo>%</mo></mrow></semantics></math></inline-formula> 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 (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>40</mn><mo>%</mo></mrow></semantics></math></inline-formula> 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. |
| first_indexed | 2024-03-10T11:03:25Z |
| format | Article |
| id | doaj.art-64775f630d4a4e84ae6b5ecf5f319f6d |
| institution | Directory Open Access Journal |
| issn | 1996-1073 |
| language | English |
| last_indexed | 2024-03-10T11:03:25Z |
| publishDate | 2021-05-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Energies |
| spelling | doaj.art-64775f630d4a4e84ae6b5ecf5f319f6d2023-11-21T21:21:54ZengMDPI AGEnergies1996-10732021-05-011411307810.3390/en14113078Large-Eddy Simulation Analyses of Heated Urban Canyon FacadesCarlo Cintolesi0Francesco Barbano1Silvana Di Sabatino2Department of Physics and Astronomy, University of Bologna, via Irnerio 46, 40126 Bologna, ItalyDepartment of Physics and Astronomy, University of Bologna, via Irnerio 46, 40126 Bologna, ItalyDepartment of Physics and Astronomy, University of Bologna, via Irnerio 46, 40126 Bologna, ItalyThermal 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 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>49</mn><mo>%</mo></mrow></semantics></math></inline-formula> 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 (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>40</mn><mo>%</mo></mrow></semantics></math></inline-formula> 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.https://www.mdpi.com/1996-1073/14/11/3078urban canyonconvective flowspollutant removalturbulencelarge-eddy simulation |
| spellingShingle | Carlo Cintolesi Francesco Barbano Silvana Di Sabatino Large-Eddy Simulation Analyses of Heated Urban Canyon Facades Energies urban canyon convective flows pollutant removal turbulence large-eddy simulation |
| title | Large-Eddy Simulation Analyses of Heated Urban Canyon Facades |
| title_full | Large-Eddy Simulation Analyses of Heated Urban Canyon Facades |
| title_fullStr | Large-Eddy Simulation Analyses of Heated Urban Canyon Facades |
| title_full_unstemmed | Large-Eddy Simulation Analyses of Heated Urban Canyon Facades |
| title_short | Large-Eddy Simulation Analyses of Heated Urban Canyon Facades |
| title_sort | large eddy simulation analyses of heated urban canyon facades |
| topic | urban canyon convective flows pollutant removal turbulence large-eddy simulation |
| url | https://www.mdpi.com/1996-1073/14/11/3078 |
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