Wind Field Characteristics Analysis Around Building Group And Numerical Simulation Of Haze-fog Particle Dispersion In Urban Areas

With the acceleration of urbanization and industrialization,urban haze-fog issues resulting from severe air pollution has caused significant harm to our residents' health and economic development of the society.The study of haze-fog diffusion from the physical view can macroscopically analyze the laws of the formation,diffusion and dissipation about the haze-fog weather in different environments,which has significant engineering meaning for the control and treatment of the urban haze-fog issues.In this thesis,literatures of simulations on the haze-fog particle dispersion are reviewed,then the basic theories of numerical simulation of particle physical dispersion are introduced,and finally the applicability of CFD simulation on haze-fog particle dispersion by comparison with wind tunnel experiments is performed.In the ANSYS Fluent 17.0 platform,wind field characteristics and haze-fog particle dispersion around a single building,a typical building group and a realistic urban area are simulated respectively,combined with the Delayed Detached Eddy Simulation turbulence model and the Discrete Phase Model method.Then laws of haze-fog particle physical dispersion are summarized.Meanwhile,the influences of turbulence models,particle diameter sizes,incoming wind directions and incoming wind velocities on the simulation results are systematically analyzed.The results show that the dispersion of haze-fog particles is mainly affected by the wind field distribution.Specifically,the wind speed mainly controls the dispersed particles velocities,while the vortex structure affects the concentration distribution in the dispersion process.When the particle diameter changes to 100 ?m,the concentration deposition during the dispersion caused by the significant gravitational effects is observed compared with the particle dispersion process for the other diameter sizes.When the wind direction changes to 22.5° and 45° respectively,the increased blockage cross-sectional area results in lower velocities around the leeward area and the changes of separation patterns cause the haze particles to have different dispersion behaviors.Different inflow velocities directly affected the vorticity distribution and the dispersion time.However,the final states of particle mass concentration distribution are almost the same.