CFD 모델을 이용한 체승 도시협곡의 흐름과 반응성 대기오염물질 확산 특성 연구
A Study on the Characteristics of Flow and Reactive Pollutants’ Dispersion in Step-up Street Canyons Using a CFD Model
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In this study, street canyons with a higher downwind building (so called, step-up street canyons) are considered for understanding characteristics of flow and reactive pollutants’ dispersion as a basic step to understand the characteristics in wider urban areas. This study used a CFD_NIMR_SNU coupled to a chemistry module just including simple NOX-O3 photochemical reactions. First, flow characteristics are analyzed in step-up street canyons with four aspect ratios (0.33, 0.47, 0.6, 0.73) defined as ratios of upwind building heights to downwind building height. The CFD_NIMR_SNU reproduced very well the main features (that is, vortices in the street canyons) which appeared in the wind-tunnel experiment. Wind speed within the street canyons became weak as the aspect ratio increased, because volume of flow incoming over the upwind building decreased. For each step-up street canyon, chemistry transport model was integrated up to 3600 s with the time step of 0.5 s. The distribution patterns of NOX and O3 were largely dependent on the mean flow patterns, however, NOX and O3 concentrations were partly affected by photochemical reactions. O3 concentration near the upwind lower region of the street canyons was much lower than background concentration, because there was much reduction in O3 concentration due to NO titration there. Total amount of NOX in the street canyons increased with the aspect ratio, resulting from the decrease of mean wind intensity.
Abstract
In this study, street canyons with a higher downwind building (so called, step-up street canyons) are considered for understanding characteristics of flow and reactive pollutants’ dispersion as a basic step to understand the characteristics in wider urban areas. This study used a CFD_NIMR_SNU coupled to a chemistry module just including simple NOX-O3 photochemical reactions. First, flow characteristics are analyzed in step-up street canyons with four aspect ratios (0.33, 0.47, 0.6, 0.73) defined as ratios of upwind building heights to downwind building height. The CFD_NIMR_SNU reproduced very well the main features (that is, vortices in the street canyons) which appeared in the wind-tunnel experiment. Wind speed within the street canyons became weak as the aspect ratio increased, because volume of flow incoming over the upwind building decreased. For each step-up street canyon, chemistry transport model was integrated up to 3600 s with the time step of 0.5 s. The distribution patterns of NOX and O3 were largely dependent on the mean flow patterns, however, NOX and O3 concentrations were partly affected by photochemical reactions. O3 concentration near the upwind lower region of the street canyons was much lower than background concentration, because there was much reduction in O3 concentration due to NO titration there. Total amount of NOX in the street canyons increased with the aspect ratio, resulting from the decrease of mean wind intensity.
참고문헌 (23)
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