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Conference Paper: Parameterization of Plume Dispersion Coefficient over Rough Surfaces
Title | Parameterization of Plume Dispersion Coefficient over Rough Surfaces |
---|---|
Authors | |
Keywords | Air pollution modeling and impact on urban inhabitants |
Issue Date | 2017 |
Citation | Urban Meteorology and Climate Conference, Hong Kong, 25-26 May 2017 How to Cite? |
Abstract | Urban air quality is an important problem nowadays because of the close proximity of
sources and receptors in dense environment. Gaussian plume models have been
commonly employed in the industry for decades. They are handy tools to estimate air
pollution impact for open-terrain configurations. However, their applications to urban
environment should be cautiously in view of the complicated recirculating flows and
turbulence generation mechanism around/over buildings. In particular, one of the key
components in Gaussian plume models, dispersion coefficient, is usually determined
empirically based on atmospheric stratification that might overlook the effect of rough
urban surfaces, resulting in prediction uncertainty.
In this paper, we report our recent study of the transport processes over idealized rough
surfaces (repeated rubs in crossflows) to simulate the flows and pollutant transport after
a ground-surface, area source in crossflows over hypothetical urban areas. The effect of
aerodynamic resistance (controlled by rib separation) on pollutant plume dispersion
(measured by vertical dispersion coefficient σz) is critically examined. Firstly,
analytical solution shows that σz is proportional to x
1/2×δ1/2×f
1/4, where x is the
downwind distance after the pollutant source, δ the turbulent boundary layer (TBL)
thickness, f (= 2uτ
2
/U∞
2
) the friction factor, uτ the friction velocity and U∞ the freestream
TBL wind speed. Afterward, a complementary approach, using both windtunnel
measurements and large-eddy simulation (LES) results, is used to verify the
newly developed theoretical hypothesis. Although mild discrepancies are observed
among various solutions (due to unaffordable scaling differences), the aforementioned
proportionality is clearly depicted. The findings unveil the weakness of conventional
practice, proposing a new parameterization of dispersion coefficient for pollutant plume
dispersion over urban areas. |
Persistent Identifier | http://hdl.handle.net/10722/247848 |
DC Field | Value | Language |
---|---|---|
dc.contributor.author | Liu, CH | - |
dc.contributor.author | Mo, Z | - |
dc.contributor.author | Wu, Z | - |
dc.date.accessioned | 2017-10-18T08:33:37Z | - |
dc.date.available | 2017-10-18T08:33:37Z | - |
dc.date.issued | 2017 | - |
dc.identifier.citation | Urban Meteorology and Climate Conference, Hong Kong, 25-26 May 2017 | - |
dc.identifier.uri | http://hdl.handle.net/10722/247848 | - |
dc.description.abstract | Urban air quality is an important problem nowadays because of the close proximity of sources and receptors in dense environment. Gaussian plume models have been commonly employed in the industry for decades. They are handy tools to estimate air pollution impact for open-terrain configurations. However, their applications to urban environment should be cautiously in view of the complicated recirculating flows and turbulence generation mechanism around/over buildings. In particular, one of the key components in Gaussian plume models, dispersion coefficient, is usually determined empirically based on atmospheric stratification that might overlook the effect of rough urban surfaces, resulting in prediction uncertainty. In this paper, we report our recent study of the transport processes over idealized rough surfaces (repeated rubs in crossflows) to simulate the flows and pollutant transport after a ground-surface, area source in crossflows over hypothetical urban areas. The effect of aerodynamic resistance (controlled by rib separation) on pollutant plume dispersion (measured by vertical dispersion coefficient σz) is critically examined. Firstly, analytical solution shows that σz is proportional to x 1/2×δ1/2×f 1/4, where x is the downwind distance after the pollutant source, δ the turbulent boundary layer (TBL) thickness, f (= 2uτ 2 /U∞ 2 ) the friction factor, uτ the friction velocity and U∞ the freestream TBL wind speed. Afterward, a complementary approach, using both windtunnel measurements and large-eddy simulation (LES) results, is used to verify the newly developed theoretical hypothesis. Although mild discrepancies are observed among various solutions (due to unaffordable scaling differences), the aforementioned proportionality is clearly depicted. The findings unveil the weakness of conventional practice, proposing a new parameterization of dispersion coefficient for pollutant plume dispersion over urban areas. | - |
dc.language | eng | - |
dc.relation.ispartof | Urban Meteorology and Climate Conference | - |
dc.subject | Air pollution modeling and impact on urban inhabitants | - |
dc.title | Parameterization of Plume Dispersion Coefficient over Rough Surfaces | - |
dc.type | Conference_Paper | - |
dc.identifier.email | Liu, CH: chliu@hkucc.hku.hk | - |
dc.identifier.authority | Liu, CH=rp00152 | - |
dc.identifier.hkuros | 281391 | - |
dc.publisher.place | Hong Kong | - |