Experimentally modelling urban air pollution and measuring turbulent dispersion
Experimentally modelling urban air pollution and measuring turbulent dispersion
The study of urban aerodynamics is a field of aerospace engineering that falls into the broader category of wind engineering. Within this field, there is interest in modelling both the dispersion of pollutants as well as the air flow around buildings. In this thesis, urban air pollution is experimentally modelled as a neutrally buoyant scalar introduced into a scale-model urban landscape. The aim of the experiments that were carried out was to obtain high-fidelity measurements of turbulent diffusion processes in idealised and realistic landscapes.
All experiments were carried out in the University of Southampton's recirculating water tunnel using simultaneous Particle Image Velocimetry (PIV) and Planar Laser Induced Fluorescence (PLIF).
The investigation into the accuracy of the PLIF technique revealed some problems in the way that attenuation is corrected for in existing PLIF studies. These were fixed in a version of a PLIF post-processing code that is aimed to be published in the future. A verification study proved the accuracy of this code by calculating the known flow rate of a scalar jet within experimental uncertainty values.
The data acquired in these experiments has provided insights into both simplified and realistic flows. The investigation into flow structures around an individual building was carried out for a case with scalar plume impingement below the leading edge stagnation point of the building. It was shown that, for this case, the scalar was drawn into the leading horseshoe vortex and formed a dual plume shape behind the building with very little vertical scalar transport. The measurements of a scalar plume in a scaled urban model showed a deflection in the direction of plume propagation from the mean flow direction. It could also be seen that the tallest buildings had a disproportionately large effect on flow fields in their local area with regard to both velocity and scalar concentration statistics.
Fluid dynamics, Urban aerodynamics, Turbulence, Scalar dispersion
University of Southampton
Rich, Tomos Jared
ff1abcf4-5e05-43e7-8b17-9517a9378938
2025
Rich, Tomos Jared
ff1abcf4-5e05-43e7-8b17-9517a9378938
Vanderwel, Christina
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Xie, Zheng-Tong
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Lim, Desmond H
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Rich, Tomos Jared
(2025)
Experimentally modelling urban air pollution and measuring turbulent dispersion.
University of Southampton, Doctoral Thesis, 134pp.
Record type:
Thesis
(Doctoral)
Abstract
The study of urban aerodynamics is a field of aerospace engineering that falls into the broader category of wind engineering. Within this field, there is interest in modelling both the dispersion of pollutants as well as the air flow around buildings. In this thesis, urban air pollution is experimentally modelled as a neutrally buoyant scalar introduced into a scale-model urban landscape. The aim of the experiments that were carried out was to obtain high-fidelity measurements of turbulent diffusion processes in idealised and realistic landscapes.
All experiments were carried out in the University of Southampton's recirculating water tunnel using simultaneous Particle Image Velocimetry (PIV) and Planar Laser Induced Fluorescence (PLIF).
The investigation into the accuracy of the PLIF technique revealed some problems in the way that attenuation is corrected for in existing PLIF studies. These were fixed in a version of a PLIF post-processing code that is aimed to be published in the future. A verification study proved the accuracy of this code by calculating the known flow rate of a scalar jet within experimental uncertainty values.
The data acquired in these experiments has provided insights into both simplified and realistic flows. The investigation into flow structures around an individual building was carried out for a case with scalar plume impingement below the leading edge stagnation point of the building. It was shown that, for this case, the scalar was drawn into the leading horseshoe vortex and formed a dual plume shape behind the building with very little vertical scalar transport. The measurements of a scalar plume in a scaled urban model showed a deflection in the direction of plume propagation from the mean flow direction. It could also be seen that the tallest buildings had a disproportionately large effect on flow fields in their local area with regard to both velocity and scalar concentration statistics.
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Published date: 2025
Keywords:
Fluid dynamics, Urban aerodynamics, Turbulence, Scalar dispersion
Identifiers
Local EPrints ID: 498832
URI: http://eprints.soton.ac.uk/id/eprint/498832
PURE UUID: dda6a45b-fcda-443c-8e46-b3b9319d4a46
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Date deposited: 03 Mar 2025 17:51
Last modified: 03 Jul 2025 02:27
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Author:
Tomos Jared Rich
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