도시 협곡에서 건물 지붕 냉각이 스칼라 물질 확산에 미치는 영향

Abstract

Abstract In this study, the effects of building-roof cooling on scalar dispersion in three-dimensional street canyons are investigated using a computational fluid dynamics (CFD)model. For this, surface temperature of building roof is systematically changed and non-reac-tive pollutants are released from street bottom in urban street canyons with the aspect ratio of1. The characteristics of flow, air temperature, and non-reactive pollutant dispersion in the con-trol experiment are analyzed first. Then, the effects of building-roof cooling are investigated bycomparing the results with those in the control experiment. In the control experiment, a portalvortex which is a secondary flow induced by ambient air flow is formed in each street canyon.Averaged air temperature is higher inside the street canyon than in both sides of the street can-yon, because warmer air is coming into the street canyon from the roof level. However, airtemperature near the street bottom is lower inside the street canyon due to the inflow of coolerair from both sides of the street canyon. As building-roof temperature decreases, wind speed atthe roof level increases and portal vortex becomes intensified (that is, downdraft, reverse flow,and updraft becomes stronger). Building-roof cooling contributes to the reduction of averageconcentration of the non-reactive pollutants and average air temperature in the street canyon.The results imply that building-roof cooling has positive effects on improvement of thermalenvironment and air quality in urban areas.Key words: CFD model, urban street canyon, building-roof cooling, non-reactive pollutant