Large-Eddy Simulation of Airflow and Pollutant Dispersion in a Model Street Canyon Intersection of Dhaka City
The atmospheric flow and dispersion of traffic exhaust were numerically studied in this work while considering a model street canyon intersection of a city. The finite volume method (FVM)-based large-eddy simulation (LES) technique in line with ANSYS Fluent have been used for flow and pollutant disp...
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| Format: | Article |
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MDPI AG
2022-06-01
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| Series: | Atmosphere |
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| Online Access: | https://www.mdpi.com/2073-4433/13/7/1028 |
| _version_ | 1797407521299759104 |
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| author | Sheikh Hassan Umma Habiba Akter Preetom Nag Md. Mamun Molla Amirul Khan Md Farhad Hasan |
| author_facet | Sheikh Hassan Umma Habiba Akter Preetom Nag Md. Mamun Molla Amirul Khan Md Farhad Hasan |
| author_sort | Sheikh Hassan |
| collection | DOAJ |
| description | The atmospheric flow and dispersion of traffic exhaust were numerically studied in this work while considering a model street canyon intersection of a city. The finite volume method (FVM)-based large-eddy simulation (LES) technique in line with ANSYS Fluent have been used for flow and pollutant dispersion modelling through the consideration of the atmospheric boundary layer (ABL). Hexahedral elements are considered for computational domain discretization in order to numerically solve problems using FVM-LES. The turbulence parameters were superimposed through a spectral synthesizer in the existing LES model through ANSYS Fluent as part of ’damage control’ due to the unsteady <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>k</mi><mo>−</mo><mi>ϵ</mi></mrow></semantics></math></inline-formula> simulation. Initially, the code is validated with an experimental study of an urban street canyon where the width and height ratio is in unity. After validation, a model urban street canyon intersection was investigated in this work. The model shows a high pollutant concentration in the intersecting corner areas of the buildings. Additionally, the study of this model intersection shows a high level of pollutant concentration at the leeward wall of downwind building in the case of increased height of an upwind building. Most importantly, it was realized from the street intersection design that three-dimensional interconnection between the dominating canyon vortices and roof level flow plays a pivotal role in pollutant concentration level on the windward walls. The three-dimensional extent of corner eddies and their interconnections with dominating vortices were found to be extremely important as they facilitate enhanced ventilation. Corner eddies only form for the streets towards the freeway and not for the streets towards the intersection. The results and key findings of this work offer qualitative and quantitative data for the estimation, planning, and implementation of exposure mitigation in an urban environment. |
| first_indexed | 2024-03-09T03:42:41Z |
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| institution | Directory Open Access Journal |
| issn | 2073-4433 |
| language | English |
| last_indexed | 2024-03-09T03:42:41Z |
| publishDate | 2022-06-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Atmosphere |
| spelling | doaj.art-a7b2194f3ffe4ad3a3eea4b8f40808ac2023-12-03T14:38:23ZengMDPI AGAtmosphere2073-44332022-06-01137102810.3390/atmos13071028Large-Eddy Simulation of Airflow and Pollutant Dispersion in a Model Street Canyon Intersection of Dhaka CitySheikh Hassan0Umma Habiba Akter1Preetom Nag2Md. Mamun Molla3Amirul Khan4Md Farhad Hasan5Department of Mathematics & Physics, North South University, Dhaka 1229, BangladeshDepartment of Mathematics & Physics, North South University, Dhaka 1229, BangladeshDepartment of Mathematics & Physics, North South University, Dhaka 1229, BangladeshDepartment of Mathematics & Physics, North South University, Dhaka 1229, BangladeshSchool of Civil Engineering, University of Leeds, Leeds LS2 9JT, UKAgriculture Victoria Research, Department of Jobs, Precincts and Regions, Victoria State Government, Melbourne, VIC 3083, AustraliaThe atmospheric flow and dispersion of traffic exhaust were numerically studied in this work while considering a model street canyon intersection of a city. The finite volume method (FVM)-based large-eddy simulation (LES) technique in line with ANSYS Fluent have been used for flow and pollutant dispersion modelling through the consideration of the atmospheric boundary layer (ABL). Hexahedral elements are considered for computational domain discretization in order to numerically solve problems using FVM-LES. The turbulence parameters were superimposed through a spectral synthesizer in the existing LES model through ANSYS Fluent as part of ’damage control’ due to the unsteady <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>k</mi><mo>−</mo><mi>ϵ</mi></mrow></semantics></math></inline-formula> simulation. Initially, the code is validated with an experimental study of an urban street canyon where the width and height ratio is in unity. After validation, a model urban street canyon intersection was investigated in this work. The model shows a high pollutant concentration in the intersecting corner areas of the buildings. Additionally, the study of this model intersection shows a high level of pollutant concentration at the leeward wall of downwind building in the case of increased height of an upwind building. Most importantly, it was realized from the street intersection design that three-dimensional interconnection between the dominating canyon vortices and roof level flow plays a pivotal role in pollutant concentration level on the windward walls. The three-dimensional extent of corner eddies and their interconnections with dominating vortices were found to be extremely important as they facilitate enhanced ventilation. Corner eddies only form for the streets towards the freeway and not for the streets towards the intersection. The results and key findings of this work offer qualitative and quantitative data for the estimation, planning, and implementation of exposure mitigation in an urban environment.https://www.mdpi.com/2073-4433/13/7/1028street canyonstreet intersectionpollutant dispersionANSYS fluentcorner eddylarge-eddy simulation (LES) |
| spellingShingle | Sheikh Hassan Umma Habiba Akter Preetom Nag Md. Mamun Molla Amirul Khan Md Farhad Hasan Large-Eddy Simulation of Airflow and Pollutant Dispersion in a Model Street Canyon Intersection of Dhaka City Atmosphere street canyon street intersection pollutant dispersion ANSYS fluent corner eddy large-eddy simulation (LES) |
| title | Large-Eddy Simulation of Airflow and Pollutant Dispersion in a Model Street Canyon Intersection of Dhaka City |
| title_full | Large-Eddy Simulation of Airflow and Pollutant Dispersion in a Model Street Canyon Intersection of Dhaka City |
| title_fullStr | Large-Eddy Simulation of Airflow and Pollutant Dispersion in a Model Street Canyon Intersection of Dhaka City |
| title_full_unstemmed | Large-Eddy Simulation of Airflow and Pollutant Dispersion in a Model Street Canyon Intersection of Dhaka City |
| title_short | Large-Eddy Simulation of Airflow and Pollutant Dispersion in a Model Street Canyon Intersection of Dhaka City |
| title_sort | large eddy simulation of airflow and pollutant dispersion in a model street canyon intersection of dhaka city |
| topic | street canyon street intersection pollutant dispersion ANSYS fluent corner eddy large-eddy simulation (LES) |
| url | https://www.mdpi.com/2073-4433/13/7/1028 |
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