UNDERSTANDING AIR EXCHANGE AND POLLUTANT DISPERSION IN A VERY LONG STREET WITH A RNG K-εMODEL
We consider a dense city as airflow and air pollutant dispersion network, comprising of streets and street intersections. Wind driven air flows in such a street network are important for removing or redistributing the airborne pollutants within the streets. Before the street network airflow can be studied, we consider the airflow problem of one street, which is a flow element in the flow network. We are interested in the relative magnitude of pollutant removal mechanisms in such long street cavity, including the air exchange due to average wind speed (ventilation) at two street ends, air exchange (ventilation) cross the open roof and turbulent exchange (transport) across the open roof. Two cases are studied with wind direction parallel (Case Ⅰ) or perpendicular (Case Ⅱ) to street axis using a computational fluid dynamics software Fluent. The street cavity is very long (1000m long, 20m wide and 20 m high). The RNG k-e turbulence model was used to consider the effect of turbulence. Results from both a wind tunnel study and a theoretical model are used to evaluate present numerical simulations. The air exchange rate (ACH), especially at roof, was calculated and compared considering the advective flow and turbulent transport The normalized concentration and mean spatial concentration were analyzed to reveal the pollutant dispersion process. For the two simulated cases, our new results show that the turbulent transport is more significant than advective term considering air exchange across the entire street roof. It is found that, although the ventilation rate for wind-parallel street was much larger than that for wind-perpendicular street (near zero), the air quality in a wind-parallel street may not be better than wind-perpendicular street because of the channel effect and pollutant accumulate effect in the former.
JIAN HANG YUGUO LI MATS SANDBERG MARKUS ROSLER LINA YANG
Department of Mechanical Engineering, The University of Hong Kong, Pokfulam, Hong Kong, China Department of Mechanical Engineering,The University of Hong Kong, Pokfulam, Hong Kong,China KTH Research School, University of Gavle, Gavle, Sweden Institute for thermodynamics and building energy system, Dresden University of Technology, Dresden,
国际会议
广州
英文
442-451
2006-12-01（万方平台首次上网日期，不代表论文的发表时间）