中文摘要：

基于榆中污染扩散实验翔实的观测资料，使用计算流体力学软件Fluent开展了城区内流场及污染物传输扩散的数值模拟研究，并将模拟值与外场实验观测值对比，以此检验Fluent软件的适用性。结果表明，Fluent能较好地模拟城区内流场，风场的模拟值能反应实际风场的变化趋势，风向平均绝对误差为32．18。，风速平均相对误差为35．63％；且模拟效果随风速的增大而逐步提高；城区建筑物对流场拖曳作用明显，街区分布对流场的影响较大；以SF6为示踪物，Fluent软件能模拟出与观测污染物扩散相似的形态，表明Fluent软件对污染物传输和扩散的较好模拟能力。该研究加深了对城区内流场复杂性的认识，并为了解城区内污染物传输扩散过程、做好空气污染事故灾害防治和救援以及事故后灾害评估等提供科学依据。

英文摘要：

The flow field and pollutant diffusion in urban areas were researched by numerical simulation with Fluent based on accurate observation data of Yuzhong pollutant diffusion experiment. Value of the simulation field and experiment observation was compared to test the applicability of Fluent, and results showed that Fluent can simulate the flow field over the complex urban terrain well. The simulated wind field had same change trend with actual wind field, with mean absolute error of the wind direction as 32.18~ and average relative error of the wind speed as 35.63%, and the simulation raised steadily with the increasing of wind speed. Also simulation results showed that the wind field was dragged obviously by city buildings, and the effects of street distribution were evident. Then drove the pollutant diffusion of sulfur hexafluoride with simulated wind field, Fluent can simulate its diffuse shape that is similar with the observed pollutant diffusion, showing that Fluent has a good ability to simulate pollutants diffusion. The complexity of the flow field in urban areas was understood deeply through this study, which can provide scientific basis for learning pollutant diffusion process in urban, handling of air pollution accident disaster, relieving and assessing accident hazard.