 |
| Titel |
Pollutant Plume Dispersion over Hypothetical Urban Areas based on Wind
Tunnel Measurements |
| VerfasserIn |
Ziwei Mo, Chun-Ho Liu |
| Konferenz |
EGU General Assembly 2017
|
| Medientyp |
Artikel
|
| Sprache |
en
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250137448
|
| Publikation (Nr.) |
 EGU/EGU2017-158.pdf |
|
|
|
|
|
| Zusammenfassung |
| Gaussian plume model is commonly adopted for pollutant concentration prediction in the
atmospheric boundary layer (ABL). However, it has a number of limitations being applied to
pollutant dispersion over complex land-surface morphology. In this study, the friction factor
(f), as a measure of aerodynamic resistance induced by rough surfaces in the engineering
community, was proposed to parameterize the vertical dispersion coefficient (σz) in the
Gaussian model. A series of wind tunnel experiments were carried out to verify the
mathematical hypothesis and to characterize plume dispersion as a function of surface
roughness as well. Hypothetical urban areas, which were assembled in the form of idealized
street canyons of different aspect (building-height-to-street-width) ratios (AR = 1/2,
1/4, 1/8 and 1/12), were fabricated by aligning identical square aluminum bars at
different separation apart in cross flows. Pollutant emitted from a ground-level
line source into the turbulent boundary layer (TBL) was simulated using water
vapour generated by ultrasonic atomizer. The humidity and the velocity (mean
and fluctuating components) were measured, respectively, by humidity sensors
and hot-wire anemometry (HWA) with X-wire probes in streamwise and vertical
directions. Wind tunnel results showed that the pollutant concentration exhibits the
conventional Gaussian distribution, suggesting the feasibility of using water vapour
as a passive scalar in wind tunnel experiments. The friction factor increased with
decreasing aspect ratios (widening the building separation). It was peaked at AR = 1/8
and decreased thereafter. Besides, a positive correlation between σz/xn (x is the
distance from the pollutant source) and f1∕4 (correlation coefficient r2 = 0.61) was
observed, formulating the basic parameterization of plume dispersion over urban areas. |
|
|
|
|
|
|