Numerical study of the effect of building configurations on tear gas dispersion

Factors such as different building shapes have an important impact on the transmission of explosive tear gas, and directly affect its simulation effect. For the study of its propagation characteristics, this paper adopts the finite element analysis and the numerical simulation method of FLUENT based on the discrete phase model (DPM), and uses the wind tunnel test to check the reliability of the numerical simulation. This paper discusses the effects of wind direction, aspect ratio and the height difference of buildings on the smoke diffusion characteristics of street canyons. The results show that as the street becomes wider, the diffusion area and airflow flux would increase, which is not conducive to the formation of high-concentration smoke areas. When the upstream windward building is higher, it can protect the downstream tear gas to a certain extent, reducing the impact of wind. When the wind speed V0 = 1 m/s, the reflux velocity is low and the smoke particles can maintain a good retention state. The highest concentration of smoke at point A of the breathing area at a wind speed of 1 m/s is 4.6 times the highest concentration at that point at a wind speed of 3 m/s, and 47.3 times the highest concentration at that point at a wind speed of 5 m/s. The study found that the influence of various working conditions on the diffusion of smoke particles can be explained by the changes of airflow field.