The air flow and pollutant concentration fields in a street canyon affected by trees could affect the comfort and health of residents. At present, the description of the non-uniform/discontinuous distribution of leaves is difficult. In this study, the leaf distribution in the canopy was characterized by establishing non-continuous (uniform/random) algorithm based on a numerical simulation method, and the effects of canopy properties including, height, porosity and uniform/random leaf distribution, on the airflow and pollutant concentration fields in urban street canyons were investigated. The position of the tree canopy was found to directly affect the airflow field form and the air velocity distribution in the street canyon at low inflows. The average air velocity in the street canyon could be reduced significantly when the top of the tree canopy is near the top of the street canyon. The air velocity and pollutant concentration in the street canyon would vary only slightly due to the canopy porosity. Due to the increasing canopy porosity, the air velocity would increase, and the pollutant concentration would be reduced. The leaves are non-continuous and uniformly distributed at constant porosity, which does not significantly change the velocity distribution and pollutant concentration in the street canyon.

受树木影响的街道峡谷中的气流和污染物浓度场可能会影响居民的舒适度和健康状况。目前，很难对叶片的不均匀/不连续分布进行描述。在这项研究中，通过建立基于数值模拟方法的非连续（均匀/随机）算法来表征冠层中的叶片分布，以及冠层特性（包括高度，孔隙率和均匀/随机叶分布）对冠层的影响。研究了城市街道峡谷的气流和污染物浓度场。发现树冠的位置直接影响气流场的形式和低流量时街道峡谷中的风速分布。当树冠顶部靠近街道峡谷顶部时，街道峡谷中的平均风速可能会大大降低。由于冠层的孔隙率，街道峡谷中的空气速度和污染物浓度只会略有变化。由于冠层孔隙度的增加，风速会增加，污染物浓度会降低。叶子是不连续的，并且在恒定的孔隙率下均匀分布，这不会显着改变街道峡谷中的速度分布和污染物浓度。