A Study on the Characteristics of Flows around Building Groups Using a CFD Model

Abstract

In this study, the characteristics of flows around building groups are investigated using a computational fluid dynamics (CFD) model. For this, building groups with different volumetric ratios in a fixed area are considered. As the volumetric ratio of the building group increases, the region affected by the building group is widened. However, the wind-speed reduced area rather decreases with the volumetric ratio near the ground bottom (z 0.7H, here, H is the height of the building group) and, above 0.7H, it increases. As the volumetric ratio decreases (that is, space between buildings was widened), the size of recirculation region decreases but flow recovery is delayed, resulting in the wider wind-speed reduced area. The increase in the volumetric ratio results in larger drag force on the flow above the roof level, consequently reducing wind speed above the roof level. However, above z 1.7H, wind speed increases with the volumetric ratio for satisfying mass conservation, resultantly increasing turbulent kinetic energy there. Inside the building groups, wind speed decreased with the volumetric ratio and averaged wind speed is parameterized in terms of the volumetric ratio and background flow speed. The parameterization method is applied to producing averaged wind speed for 80 urban areas in 7 cities in Korea, showing relatively good performance.

Impacts of Urban Layouts and Open Space on Urban Ventilation Evaluated by Concentration Decay Method

“…For three-dimensional UCL geometries, the plan area index λ p and frontal area index λ f [4][5][6]9,10] are regarded as the key urban parameters to influence the flow and pollutant dispersion in urban areas. In addition, the other factors including overall urban form and ambient wind directions [2,3,[6][7][8][9], building height variations [5,[20][21][22][23][24][25], thermal buoyancy force for weak-wind atmospheric conditions [10,18,[26][27][28][29][30], etc. also play significant roles in the flow and pollutant dispersion in UCL models.…”