T型街谷交叉路口机动车诱导下污染物传播规律

为了探究车辆转弯行驶对于T型街谷交叉路口处空气流动以及污染物扩散的影响,本文建立了该系统中车辆移动下空气流动与污染物传播耦合数学模型,采用计算流体力学方法,揭示T型街谷交叉路口处车辆诱导下的机械湍流特性,并且基于场协同理论量化了车速对污染物扩散的影响.结果表明,在不同速度的转弯过程中,转弯速度增加使得车辆诱导的湍动能也随之增加.车速为9m/s时车辆中轴线湍动能最大值是车速为3m/s时的5倍.但是完成转弯行驶瞬时车辆尾部湍动能的影响长度不变(约为4m).车速由3m/s增加至9m/s时,场协同数增加了66%,行人区内污染物平均浓度降低了43%.车辆转弯行驶速度增加,改变了T型街谷交叉路口处流场结构,速度场与污染物浓度场之间的协同作用增强,提高了行人区内污染物对流扩散效果,使得污染物浓度降低.

Numerical simulation of pollutant dispersion induced by vehicle moving in a T-shaped intersection

In order to explore the influence of the moving vehicle on the air flow and pollutant dispersion at the T-shaped street intersection, a mathematical model coupling the fluid and pollutant concentration fields with the moving vehicle is established. The characteristics of the traffic-induced turbulence and pollutant diffusion in the T-shaped street intersection are revealed using the method of computational fluid dynamics. Based on filed synergy theory, the impact of the vehicle moving speed on pollutant dispersion is quantitatively evaluated. The results show that the turbulent kinetic energy induced by the moving vehicle increases with the increase of the vehicle speed. When the vehicle speed is 9m/s, the maximum turbulent kinetic energy on the central axis of the vehicle is 5times higher than that when the vehicle speed is 3m/s. However, the affected region of the turbulent kinetic energy in the rear of the vehicle is about 4m for all the cases. When the vehicle speed increases from 3m/s to 9m/s, the field synergy increases by 66%, and the average concentration of pollutants in the pedestrian area decreases by 43% With the increase of vehicle moving speed, the flow field at T-shaped street intersection is changed, and the synergistic effect between the velocity field and the pollutant concentration field is enhanced, which in turn reduces the pollutant concentration by improving the convective mass transfer effect in the pedestrian region.