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Implementing spatial variance in the rate of photolytic breakdown of NO2 in urban street canyons

Friberg, Fabian LU (2022) MVKM01 20202
Department of Energy Sciences
Abstract
In this study a module for calculating the solar exposure of individual fluid cells
was developed to more accurately represent the effect of photolysis on the pollutant
dispersion in an urban street canyon. The module was tested and validated on 12
different cases, each with a different geographical location, time of year and/or time
of day. It was used for four parallel simulations performed on a street canyon model
representing a real-life street canyon in Gothenburg, Sweden, each one using a differ-
ent model for NO2 photolysis. NOx and O3 levels were measured and compared at
street level, mid-canyon level, and sky level, with results showing negligible differ-
ence between models using partial sunlight and no sunlight, while... (More)
In this study a module for calculating the solar exposure of individual fluid cells
was developed to more accurately represent the effect of photolysis on the pollutant
dispersion in an urban street canyon. The module was tested and validated on 12
different cases, each with a different geographical location, time of year and/or time
of day. It was used for four parallel simulations performed on a street canyon model
representing a real-life street canyon in Gothenburg, Sweden, each one using a differ-
ent model for NO2 photolysis. NOx and O3 levels were measured and compared at
street level, mid-canyon level, and sky level, with results showing negligible differ-
ence between models using partial sunlight and no sunlight, while showing signifi-
cant difference between the partial sunlight model and the uniform sunlight model.
We conclude from our results that simulations without any modeling of photolytic
reactions are sufficient for accurately predicting NO and O3 levels, but fail to accu-
rately predict NO2 levels, while simulations utilizing a solar model with uniform
photolysis throughout the simulated domain are sufficient for accurately predicting
NO and NO2 levels, but fail to accurately predict O3 levels. For any study placing an
emphasis on both NO2 and O3 levels within the domain, it is our recommendation to
incorporate a non-uniform solar model. Such a model was developed for this thesis,
and aims to be integrated into the OpenFOAM framework in the future. (Less)
Popular Abstract
The dispersion of NOx gases in a turbulent street canyon was simulated using different sunlight models. The simulation modelled for wind, pressure, temperature, reaction speed, solar intensity and solar movement, using a reduced chemical reaction space of 3 main equations involving nitrogen oxide, nitrogen dioxide and ozone. The aim of this paper is to assist urban developers in planning street construction, reducing citizen exposure to harmful gases in the city air. The simulation was performed using the open source CFD platform OpenFOAM. A module for calculating the solar exposure of individual fluid cells
was developed to more accurately represent the effect of photolysis on the pollutant
dispersion in an urban street canyon. The... (More)
The dispersion of NOx gases in a turbulent street canyon was simulated using different sunlight models. The simulation modelled for wind, pressure, temperature, reaction speed, solar intensity and solar movement, using a reduced chemical reaction space of 3 main equations involving nitrogen oxide, nitrogen dioxide and ozone. The aim of this paper is to assist urban developers in planning street construction, reducing citizen exposure to harmful gases in the city air. The simulation was performed using the open source CFD platform OpenFOAM. A module for calculating the solar exposure of individual fluid cells
was developed to more accurately represent the effect of photolysis on the pollutant
dispersion in an urban street canyon. The module was tested and validated on 12
different cases, each with a different geographical location, time of year and/or time
of day. It was used for four parallel simulations performed on a street canyon model
representing a real-life street canyon in Gothenburg, Sweden, each one using a differ-
ent model for NO2 photolysis. The results showed that the effects of sunlight are highly localized, and so correct modelling on sunlight levels at the points of measurement will be sufficient for most simulations trying to account for photolytic effect. However, for higher accuracy it is recommended to utilize the solar module developed in this paper for accurate results. (Less)
Please use this url to cite or link to this publication:
author
Friberg, Fabian LU
supervisor
organization
course
MVKM01 20202
year
type
H2 - Master's Degree (Two Years)
subject
keywords
cfd, computational fluid dynamics, NOx, street canyon, NO2, NO, O3, photolysis, OpenFOAM
report number
ISRN: LUTMDN/TMHP-22/5493-SE
ISSN
0282-1990
language
English
id
9078414
alternative location
https://www.overleaf.com/read/mtntmznmtrqv
date added to LUP
2022-04-19 09:12:54
date last changed
2022-04-19 09:12:54
@misc{9078414,
  abstract     = {{In this study a module for calculating the solar exposure of individual fluid cells
was developed to more accurately represent the effect of photolysis on the pollutant
dispersion in an urban street canyon. The module was tested and validated on 12
different cases, each with a different geographical location, time of year and/or time
of day. It was used for four parallel simulations performed on a street canyon model
representing a real-life street canyon in Gothenburg, Sweden, each one using a differ-
ent model for NO2 photolysis. NOx and O3 levels were measured and compared at
street level, mid-canyon level, and sky level, with results showing negligible differ-
ence between models using partial sunlight and no sunlight, while showing signifi-
cant difference between the partial sunlight model and the uniform sunlight model.
We conclude from our results that simulations without any modeling of photolytic
reactions are sufficient for accurately predicting NO and O3 levels, but fail to accu-
rately predict NO2 levels, while simulations utilizing a solar model with uniform
photolysis throughout the simulated domain are sufficient for accurately predicting
NO and NO2 levels, but fail to accurately predict O3 levels. For any study placing an
emphasis on both NO2 and O3 levels within the domain, it is our recommendation to
incorporate a non-uniform solar model. Such a model was developed for this thesis,
and aims to be integrated into the OpenFOAM framework in the future.}},
  author       = {{Friberg, Fabian}},
  issn         = {{0282-1990}},
  language     = {{eng}},
  note         = {{Student Paper}},
  title        = {{Implementing spatial variance in the rate of photolytic breakdown of NO2 in urban street canyons}},
  year         = {{2022}},
}