Study on the Law of Diffusion of Sudden Pollutants in Subway Ventilation Shaft

The underground subway stations have become the targets of terrorism due to the features of staff-intensive and poor ventilation. In the present study, the dynamic mesh model was used to predict the dynamic change of the flow field in the tunnel induced by the train motion. The DPM model was employed to simulate the interaction between the continuous phase of the air and the discrete phase of pollution particles. Accordingly, the dispersion of sudden pollutants released in the ventilation shaft was investigated. The results show that the submicron particles have a good following performance with the air. The dispersion characteristics of the particles highly depend on the unsteady flow field in the tunnel, which is significantly affected by the piston effect induced by the train motion. It can be concluded that particle diffusion experiences three stages: vertical forward and reverse diffusion in the wind shaft, vertical positive diffusion in the wind shaft, and longitudinal stable diffusion in the interval tunnel. It hopes that the study can provide guides for future biochemical protection in the subway system.