Atmosphere (대기)

Korean Meteorological Society (한국기상학회)
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A Study on the Characteristics of Flow and Reactive Pollutants' Dispersion in Step-up Street Canyons Using a CFD Model

CFD 모델을 이용한 체승 도시협곡의 흐름과 반응성 대기오염물질 확산 특성 연구

  • Kim, Eun-Ryoung (Department of Environmental Atmospheric Sciences, Pukyong National University) ;
  • Park, Rokjin J. (School of Earth and Environmental Sciences, Seoul National University) ;
  • Lee, Dae-Geun (Applied Meteorology Research Division, National Institute of Meteorological Research) ;
  • Kim, Jae-Jin (Department of Environmental Atmospheric Sciences, Pukyong National University)
  • 김은령 (부경대학교 환경대기과학과) ;
  • 박록진 (서울대학교 지구환경과학부) ;
  • 이대근 (국립기상과학원 응용기상연구과) ;
  • 김재진 (부경대학교 환경대기과학과)
  • Received : 2015.03.25
  • Accepted : 2015.06.16
  • Published : 2015.09.30
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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 $NO_X-O_3$ 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 $NO_X$ and $O_3$ were largely dependent on the mean flow patterns, however, $NO_X$ and $O_3$ concentrations were partly affected by photochemical reactions. $O_3$ concentration near the upwind lower region of the street canyons was much lower than background concentration, because there was much reduction in $O_3$ concentration due to NO titration there. Total amount of $NO_X$ in the street canyons increased with the aspect ratio, resulting from the decrease of mean wind intensity.

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References

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