On the effects of walking speed, crowd density and human-to-source distance on pollutant dispersion in indoor spaces
On the effects of walking speed, crowd density and human-to-source distance on pollutant dispersion in indoor spaces
The effects of walking speed, crowd density and human-to-source distance on pollutant dispersion in two scaled room models are investigated using simultaneous planar laser-induced fluorescence and particle-image velocimetry techniques. For a small 3 m high room, where the length-scales of the people and room are comparable, the walking motions significantly influenced the macro room mean flow patterns. This has a strong effect on the scalar dispersion properties as the magnitudes of the advective scalar fluxes are often comparable or larger than the turbulent scalar fluxes. As such, the scalar dispersion properties are case specific. For a large 9 m high room, the walking motion influenced only the local mean flow field. The increase in walking speed and crowd density improves the efficiency in which the scalar is transported and mixed with fresh ambient fluid out of the measurement plane (i.e. along the direction of the motion), leading to scalar-free zones observed on the opposite side of the room from the ventilation outlet. The area of the scalar-free zone increases with an increase in the walking speed and crowd density. The advective scalar fluxes are more sensitive to the human motion than the turbulent components, and as the mixing efficiency improves, the advective fluxes show a greater weakening with increased distance from source. The concentration PDFs in the near-source region can be described by the exponential function where the expected value at the 99% percentile can be derived as C
99/c
rms
′=4.61, which agreed well with the experimental measurements of 4.1 to 5.9.
Crowd effects, Indoor air quality, Indoor airflow, Risk assessment, Scalar dispersion
Lim, H.D.
81fc08e5-a8ff-4933-b873-a1b4aab3b72e
Foat, Timothy G.
eddebff8-0a58-4a9a-a2ec-45563e965245
Parker, Simon T.
ff55386a-2a0b-4af2-81dd-b8674e9be344
Vanderwel, Christina
fbc030f0-1822-4c3f-8e90-87f3cd8372bb
1 July 2024
Lim, H.D.
81fc08e5-a8ff-4933-b873-a1b4aab3b72e
Foat, Timothy G.
eddebff8-0a58-4a9a-a2ec-45563e965245
Parker, Simon T.
ff55386a-2a0b-4af2-81dd-b8674e9be344
Vanderwel, Christina
fbc030f0-1822-4c3f-8e90-87f3cd8372bb
Lim, H.D., Foat, Timothy G., Parker, Simon T. and Vanderwel, Christina
(2024)
On the effects of walking speed, crowd density and human-to-source distance on pollutant dispersion in indoor spaces.
Building and Environment, 259, [111649].
(doi:10.1016/j.buildenv.2024.111649).
Abstract
The effects of walking speed, crowd density and human-to-source distance on pollutant dispersion in two scaled room models are investigated using simultaneous planar laser-induced fluorescence and particle-image velocimetry techniques. For a small 3 m high room, where the length-scales of the people and room are comparable, the walking motions significantly influenced the macro room mean flow patterns. This has a strong effect on the scalar dispersion properties as the magnitudes of the advective scalar fluxes are often comparable or larger than the turbulent scalar fluxes. As such, the scalar dispersion properties are case specific. For a large 9 m high room, the walking motion influenced only the local mean flow field. The increase in walking speed and crowd density improves the efficiency in which the scalar is transported and mixed with fresh ambient fluid out of the measurement plane (i.e. along the direction of the motion), leading to scalar-free zones observed on the opposite side of the room from the ventilation outlet. The area of the scalar-free zone increases with an increase in the walking speed and crowd density. The advective scalar fluxes are more sensitive to the human motion than the turbulent components, and as the mixing efficiency improves, the advective fluxes show a greater weakening with increased distance from source. The concentration PDFs in the near-source region can be described by the exponential function where the expected value at the 99% percentile can be derived as C
99/c
rms
′=4.61, which agreed well with the experimental measurements of 4.1 to 5.9.
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Accepted/In Press date: 14 May 2024
e-pub ahead of print date: 16 May 2024
Published date: 1 July 2024
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© 2024 The Authors
Keywords:
Crowd effects, Indoor air quality, Indoor airflow, Risk assessment, Scalar dispersion
Identifiers
Local EPrints ID: 490321
URI: http://eprints.soton.ac.uk/id/eprint/490321
ISSN: 0360-1323
PURE UUID: 3bcb26da-b3dc-4723-a862-271b9a450602
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Date deposited: 23 May 2024 16:47
Last modified: 12 Jul 2024 01:52
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Author:
H.D. Lim
Author:
Timothy G. Foat
Author:
Simon T. Parker
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