Dispersion of coughed droplets in a fully-occupied high-speed rail cabin

The dispersion process of respiratory droplets released by coughing of an individual in a high speed rail cabin is studied using CFD simulations. The cabin is fully-occupied by 48 passengers with a seating arrangement of 12 rows and 4 columns. Four cases of different boundary conditions of air supply and exhausts are studied. The droplets dispersion characteristics and the maximum dispersion distances under specified ventilation conditions are studied. All 48 passengers are simulated by relatively realistic three-dimensional thermal manikins. The coughing individual is located on an aisle seat in the seventh row. The duration of a single cough is assumed to be 0.4 s; and a time-dependent coughing velocity profile is used. Within the first 10 s after coughing, a separation phenomenon of the so-called “old” and “new” droplets is observed. The “old” droplets generated in the first 0.2 s escaped from the body plume, and were injected into the lower zone of the cabin. These droplets stayed longer in the lower zone of the cabin. The “new” droplets generated in the next 0.2 s, had a relatively small velocity, and thus followed the upward body plume, entering directly the upper zone. The luggage rack also has an effect on the airflow patterns in the HSR cabin. The droplets removal ability is stronger when there is a through flow from the front door to back. However, in this situation, the droplets can disperse much further and affect more passengers.