Influence of boundary inflow wind fluctuation on simulated urban atmospheric diffusion
DONG Long-xiang1,2, ZUO Hong-chao1, YANG Bin1, CHEN Ji-wei3, MA Kai-ming3, YU Ye2
1. Key Laboratory for Semi-Arid Climate Change, Ministry of Education, College of Atmospheric Sciences, Lanzhou University, Lanzhou 730000, China;
2. Key Laboratory for Land Process and Climate Change in Cold and Arid Regions, Northwest Institute of Eco-Environment and Resource, Chinese Academy of Sciences, Lanzhou 730000, China;
3. Unit of 93811 of Pepole's Liberation Army, Lanzhou 730020, China
The impact of the inflow wind fluctuation (i.e. wind velocity and wind speed) on the urban pollutant dispersion from a point source released at ground level under neutral stratification was analyzed using the computational fluid dynamics (CFD) model Fluent, where the boundary inflow conditions were provided in the form of wind velocity and turbulence profiles. Results suggested that the CFD model could reproduce the characteristic flow pattern (e.g. vortex, channeling, and so on) observed in actual urban environment, and the simulated wind velocity, wind direction and turbulence kinetic energy were in good agreement with observations. The results from a set of sensitivity experiments showed that the flow field and turbulent kinetic energy as well as the spatial distribution of pollutants in the urban area were very sensitive to the fluctuation of inflow wind speed and wind direction. This may be one of the main reasons for the inconsistency between the observed and the simulated concentrations in previous studies. Therefore, the uncertainty of boundary inflow should be considered in future simulation studies on urban atmospheric diffusion.
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