The microenvironment, which involves pollutant dispersion of the urban street canyon, is critical to the health of pedestrians and residents. The objectives of this work are twofold: (i) to effectively assess the pollutant dispersion process based on a theory and (ii) to adopt an appropriate stratigy, i.e., wind catcher, to alleviate the pollution in the street canyons. Pollutant dispersion in street canyons is essentially a convective mass transfer process. Because the convective heat transfer process and the mass transfer process are physically similar and the applicability of field synergy theory to turbulence has been verified in the literature, we apply the field synergy theory to the study of pollutant dispersion in street canyons. In this paper, a computational fluid dynamics (CFD) simulation is conducted to investigate the effects of wind catcher, wind speed and the geometry of the street canyons on pollutant dispersion. According to the field synergy theory, Sherwood number and field synergy number are used to quantitatively evaluate the wind catcher and wind speed on the diffusion of pollutants in asymmetric street canyons. The results show that adding wind catchers can significantly improve the air quality of the step-down street canyon and reduce the average pollutant concentrations in the street canyon by 75%. Higher wind speed enhances diffusion of pollutants differently in different geometric street canyons.

涉及城市街道峡谷污染物扩散的微环境对行人和居民的健康至关重要。这项工作的目标是双重的：（i）根据一种理论有效地评估污染物的扩散过程，以及（ii）采取适当的策略，即采用捕风器，以减轻街道峡谷的污染。街道峡谷中的污染物扩散本质上是对流传质过程。由于对流换热过程和传质过程在物理上是相似的，并且已经在文献中验证了场协同理论在湍流中的适用性，因此我们将场协同理论应用于研究街道峡谷中的污染物扩散。在本文中，进行了计算流体动力学（CFD）仿真，以研究捕风器，风速和街道峡谷的几何形状对污染物扩散的影响。根据场协同理论，舍伍德数和场协同数用于定量评估不对称街道峡谷中捕风者和风速对污染物扩散的影响。结果表明，添加捕风器可以显着改善台阶式街道峡谷的空气质量，并使街道峡谷中的平均污染物浓度降低75％。更高的风速在不同的几何街道峡谷中以不同方式增强了污染物的扩散。Sherwood数和场协同数用于定量评估不对称街道峡谷中捕风者和风速对污染物扩散的影响。结果表明，添加捕风器可以显着改善台阶式街道峡谷的空气质量，并使街道峡谷中的平均污染物浓度降低75％。更高的风速在不同的几何街道峡谷中以不同方式增强了污染物的扩散。Sherwood数和场协同数用于定量评估不对称街道峡谷中捕风者和风速对污染物扩散的影响。结果表明，添加捕风器可以显着改善台阶式街道峡谷的空气质量，并使街道峡谷中的平均污染物浓度降低75％。更高的风速在不同的几何街道峡谷中以不同方式增强了污染物的扩散。