Abstract:A street level computational fluid dynamics (CFD) model was established to simulate the movement characteristics of the released gas and the concentration distribution around the complex arrangement of buildings. A wind tunnel experiment about release and dispersion in building array was used to validate the model. Then numerical simulations were carried out with two different reference wind speeds, 1.5 m?s-1 and 3.0 m?s-1, in a genuine urban area. The results show that, given appropriate parameters, the RNG k—ε closure and SIMPLE algorithm can be employed to predict the dispersion process accurately in obstacle terrain. The time varying concentration distributions near the ground highlight the influences of wind speed, road and building arrangement, on the dispersion. The sampling concentration around buildings is strongly affected by the positions of sampling points relative to source, including height, distance from the source, angle from wind direction, and so on. The higher wind velocity speeds up plume propagation, as well as concentration dilution process. The results also confirm that, among dense buildings the hazardous gas may stay much longer, which constitutes a threat to public health and safety.
