Although several studies on the dispersion of heavy toxic gas released from ruptured tanks on vehicles during transportation have considered complex terrain such as urban buildings, the influence of trees on the flow field in urban areas during gas dispersion tends to be ignored. In this study, a Computational Fluid Dynamics (CFD) model was proposed to investigate the characteristics of gas release and dispersion from loaded vehicle in the urban environment. In this model, the tree crown was treated as a porous medium, and the influence of drag due to the crown was incorporated into the model by a momentum source term through a user-defined function. In this study, the dynamic characteristics of chlorine (Cl₂) dispersion under the conditions of building distribution, tree species and porosities were comprehensively analysed, to cover the influence of urban complexity, leaf density, and tree planting configuration. The results show that compared with flat terrain, the presence of urban buildings will prolong the dense gas retention time and increase the dangerous distance. It is found that the horizontal dispersion distance can increase by 63% and the isosurface of 25 ppm hazardous gas can increase by 130% with the introduction of buildings. Compared with the terrain with only buildings, the introduction of arbors or shrubs can result in a 147% or 359% increase in the maximum concentration. Also, trees will prolong the dispersion duration. It is also found that the higher the porosity, the less the wind blocking effect, and the weaker the ability of capturing gas. The wind field affected by arbores and shrubs are different in height, and arbores capture more Cl₂. Planting short shrubs around buildings can effectively reduce the spread of harmful gases.

虽然一些关于运输过程中车辆破裂罐释放的重毒气体扩散的研究考虑了城市建筑物等复杂地形，但气体扩散过程中树木对城市流场的影响往往被忽略。在这项研究中，提出了计算流体动力学 (CFD) 模型来研究城市环境中装载车辆的气体释放和扩散特性。在该模型中，树冠被视为多孔介质，树冠阻力的影响通过用户定义的函数通过动量源项合并到模型中。本研究中，氯（Cl ₂) 对建筑分布、树种和孔隙度条件下的分散性进行了综合分析，以涵盖城市复杂性、叶密度和植树配置的影响。结果表明，与平坦地形相比，城市建筑物的存在会延长浓气滞留时间，增加危险距离。结果表明，随着建筑物的引入，水平扩散距离可增加63%，25 ppm有害气体的等值面可增加130%。与只有建筑物的地形相比，乔木或灌木的引入可导致最大浓度增加147%或359%。此外，树木会延长分散持续时间。还发现孔隙率越高，挡风效果越小，捕集气体的能力越弱。乔木和灌木影响的风场高度不同，乔木捕获的Cl较多₂ . 在建筑物周围种植矮灌木，可以有效减少有害气体的传播。