| Summary: | 碩士 === 淡江大學 === 水資源及環境工程學系 === 84 === Carbon monoxide distribution in street canyons under
various geometry''s,atmospheric stability, temperature gradient
induced buoyant effect and trafficload were simulated. We
intend to use the simulation results to evaluatepedestrian
pollutant exposure and to provide external conditions
forevaluating indoor air quality of the buildings beside urban
street. In thisstudy, we consider several factors those may
affect the pollutant distributionin street canyons. The
considered factors include geometry of the streetcanyons,
atmospheric stability, traffic load and turbulent buoyant
effect. Atwo-dimensional domain that includes suburban
roughness and urban streetcanyons was considered as the
simulation domain. The considered influentialfactors were
imposed into the simulation through the associated
boundaryconditions. The simulated results show that serious
pollutant accumulationoccurred at where double vortices
encountered and the situation only occurredat specific aspect
ratios of the street canyons. Usually, the stagnation
zoneformed at where the encounter of two vortices that reduce
the transport ofpollutant and the pollutant tent to accumulate
at the region. Buoyant effectto the vortices formation was
found that the double vortices occurred atsmaller aspect
ratio of the canyons with buoyancy than those without buoyancy.
The buoyant effect also change the pollutant transport pattern
in the canyons.The pedestrian exposure to the street air
pollutant under various trafficloads and atmospheric stability
were evaluated. This study concluded that thepatterns of
pollutant distribution in different street canyons are
mostlyaffected by their aspect ratios where the affect of
buoyancy and atmosphericstability played less role. The
pedestrian exposure to the street airpollution is considered
to be serious under specific conditions when
pollutantconcentrations at 3 m above ground level are very
high. Those specificconditions were also found in this study.
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