Dependence of City Ventilation by Thermal Buoyancy on Thermal Stratification
Atmospheric stability is quite important on the heat removal and dispersion of air pollutants in urban area. But the existing numerical studies on this subject are limited. The effects of thermal stratification on air flows in city street canyons were studied using stratified inlet airflow. Two simple Hong Kong city models with complex terrain were considered here for modelling the city ventilation of a whole city under different atmospheric conditions. A 3D RNG k-ε turbulent model was used for the numerical simulation. The results showed that the influence of thermal stratification can be significant on the city ventilation by thermal buoyancy. For a simple model I, when the wind speed is relatively large, the impact of thermal stratification on the airflow in the city street canyons is minor. When the wind speed is smaller relative to the buoyancy force, the airflow in the street canyons is depended on the thermal stratification. The greater the instability, the stronger the vertical mix and bigger the normalized flow rate by turbulent fluctuation. For the model II, the influence of thermal stratification is strong under relative strong background wind. The study can provide a good understanding of urban ventilation by thermal buoyancy and useful information for urban planning.
Thermal stratification City ventilation Thermal buoyancy CFD simulation
Lina Yang Yuguo Li
Department of Mechanical Engineering,the University of Hong Kong,Hong Kong SAR,China
国际会议
The 6th International Symposium on Heating,Ventilating and Air Conditioning(第六届国际暖通空调学术会议)
南京
英文
1144-1151
2009-11-06（万方平台首次上网日期，不代表论文的发表时间）