# Study on the Impact of Ventilation Methods on Droplet Nuclei Transmission in Subway Carriages
## 1 Introduction
[PERSON] [22] revealed the key mechanisms of droplet dispersion in subway cars through CFD numerical simulations. It was found that the position of the infected person significantly affected the ventilation efficiency. This suggests that the airflow organization of the ventilation system needs to be differentiated for the different zones. Similar studies include those by [PERSON] [23], who used CFD simulations to analyze the dispersion of cough-generated droplets in aircraft cabins, a key concern in aviation epidemiology. The results demonstrated that decreased ventilation rates led to an increased dispersion range of droplets throughout the cabin. In order to ascertain the impact of various ventilation configurations, air change rates, breathing patterns, and supply air temperatures on cross-exposure and infection risk were analyzed. [PERSON] [24] found that in the aircraft cabin, air pollutant transport via airflow is greatly influenced by the differences in passengers breathing and area pollutant concentration evaluation of cross-infection. The results show that the seating layout has a significant impact on pollutants. [PERSON] et al. [25] used CFD simulations to study the transport and evaporation processes of multicomponent cough droplets under different ventilation configurations in hospital wards. The influence of exhaust vent positioning on droplet removal efficacy was examined, and an optimized vent location was recommended to enhance the extraction of droplets from indoor air. [PERSON] et al. [26] performed an investigation on individual exposure in thermally stratified meeting rooms at varying airflow speeds. Their findings suggested that with increased airflow, exposure may become less reliant on the source's position. [PERSON] et al. [27] examinedthe impact of various airflow dispersion techniques on infection probability. Their findings indicated that the position of the affected individual significantly influences the probability of infection in both displacement and wall-mounted ventilation systems. Nevertheless, the latter demonstrated a more significant impact. [PERSON] et al. [28] considered two key parameters, with the purpose of exploring the transmission of virus-containing droplets in a dynamic indoor environment, with a particular focus on the interaction between human movement speed and the distance between people. The results indicate that human movement speed and distance affect the size and direction of indoor airflow, influencing the suspension and diffusion of droplets of different sizes, and significantly increase the infection risk for susceptible individuals. [PERSON] et al. [29] pointed out that the use of physical barriers can effectively block exhalation, thereby preventing droplet and airborne transmission over short distances between individuals. Compared to the situation without barriers, the presence of cross and linear barriers increases the concentration within the compartment by an average of 97.2% and 25.5%. Previous studies have examined the functionality of MV systems, but most of these have focused on the effects of changing the supply and return air vent positions or the location of infected individuals. Many issues still remain unresolved. These issues can be divided into two main themes, the aim being to verify the accuracy of the model assumptions and the simulation scenarios. The use of tracer gas-wrapped droplets in the form of tracer gas provides intuition in terms of visualization and enables a more direct view of the distance of droplet spreading. The study concluded that the better ventilation method is the SFRC air supply method, which can effectively inhibit the spread of droplets. The researchers quantitatively analyzed the arrival distance of particles to determine a safe distance from the infected person in the carriage and assessed the risk of infection in the carriage.