# Droplets Transmission Mechanism in a Commercial Wide-Body Aircraft Cabin
###### Abstract  
COVID-19 is a respiratory infectious disease that spreads readily between people, and an urgent issue of passengers' exposure risk assessment in commercial aircraft has been raised because an aircraft cabin as a confined space may carry and transmit the disease worldwide. In this study, the droplets transmission process under different ventilation systems in a twin-aisle wide-body aircraft was studied using CFD simulations and the infection risk of passengers was assessed by the improved Wells-Riley model. Numerical results found that the transmission mechanism of droplets in the aircraft cabin was different depending on the type of ventilation systems and the location of the infectious source. Annular airflow could effectively enhance the ability of droplets transmission, while direct airflow, represented by displacement ventilation, could significantly inhibit droplets transmission. Accordingly, a new type of ventilation system was proposed based on the concept that the overall space is organized by annular airflow and the local area is direct airflow. Compared with sidewall mixing ventilation system, the infection risk of the new ventilation system presented in this study is reduced by 27%. aircraft cabin; ventilation system; droplets transmission; infection risk; numerical simulation +
Footnote †: journal: Medical  
under the existing ventilation system. [PERSON] et al. [8] point out that researchers could gain a deeper understanding of disease transmission in the aircraft cabin through a mathematical model of infection risk. [PERSON] et al. [9] performed retrospective analysis on a tuberculosis epidemic on a commercial aircraft and the infection risks of the passengers were assessed using the dose-response model. [PERSON] [10] computed the transmission of the droplets exhaled by the infectious source seated in the middle of a seven-row twin-aisle cabin and found that the airflow pattern in the cabin played the most important role on the droplets transport. [PERSON] [11] conducted some experiments to study the transmission of expiratory aerosols in an aircraft cabin mock-up. The study suggested that a higher supply airflow rate improved the dilution and reduced the infection risks of passengers seated close to the source, but the aerosol dispersion was enhanced[PERSON] [PERSON] et al. [12] studied the transmission characteristics of airborne droplets and the infection risks of passengers under the mixing ventilation system using a Boeing 737 cabin model. The study found that the spread of particles was related to the release locations. Then, [PERSON] et al. [13; 14] evaluated the effects of cough-jet on instantaneous cough contaminants transport characteristics in passenger's local environments and found that cough flow could increase the residence times of contaminants. Additionally, the conclusion that the droplets released by passengers located in different positions have different effects on other passengers was re-emphasized. [PERSON] et al. [15] found that the infection risks of passengers under displacement ventilation system was lower than that under mixing ventilation system and the infection risk could be reduced when passengers wore masks. In order to regulate the cabin environment on aircrafts, intervention measures [16] and innovative ventilation systems [17] were proposed. Unfortunately, [PERSON] et al. did not consider the performance of the new ventilation system when the infectious source was located in different locations. In addition, the transmission of droplets of different sizes generated by talking, coughing and breathing activities in a cabin was also studied [18]. At present, there has been little research on reducing the infection risk of passengers by improving the ventilation system. Additionally, the air flow organization optimization aimed at improving the removal efficiency of pollutant and reducing pollutants in passengers' breathing areas was mostly carried out by using gaseous pollutants representing droplets [19; 20; 21; 22].