Numerical Investigation of Pathogen Transmission Via Cough Droplets in Aircraft Cabins and Mechanism for Transmission Control

Abstract

Aircraft cabin ventilation systems play a vital role in ensuring not only a continuous supply of fresh air but also effective control of air distribution and reduction of airborne pathogen contamination in passengers' breathing zones. Therefore, assessing environmental parameters such as velocity magnitude, airflow path, and recirculation zones across various ventilation systems is essential. Contamination in the form of cough droplets requires careful evaluation and distribution inside the aircraft cabin as they are the main reason for infection spread. Computational Fluid Dynamics (CFD) models of aircraft cabins offer a virtual solution for understanding physical phenomena, such as the airflow distribution within an aircraft ventilation system. Using these models, researchers can study and comprehend the system while minimizing costs and time compared to experimental setups. A generic single-aisle cabin of a regional jet aircraft has been modelled, and CFD simulations are performed using ANSYS FLUENT with a k-omega Shear Stress Transport (SST) turbulence model with enhanced wall treatment. The aircraft cabin is simplified to a cross-section representing one row of three seats of human manikins, which are modelled to represent passengers abreast. A periodic boundary condition is applied to mimic the entire length of the cabin. This approach helps reduce meshing complexity and computational cost while still capturing relevant airflow behaviour. A typical cough jet is imposed along with droplets for a specified time duration to assess the model for the strongest possible cough scenario. This research examines various aircraft cabin ventilation systems using CFD to analyse airflow distribution and the transport of contaminants within the cabin. The pathogen spread in existing ventilation systems shows a greater possibility of infection spread as the cough droplets reach the breathing zones of co-passengers travelling with the infected person. Several control device concepts are designed and evaluated using the simulation technique to select the best-performing concept. The flow path of the device is further optimized using the design of experiments method to achieve the least pressure drop and maximum flow spread and velocity. The particle swarm optimization algorithm is deployed to cross-verify the optimized design variables for the final design. vii A newly designed control device is attached to existing gaspers, and the performance is evaluated through cabin-level simulations to estimate the pathogen spread control. The device could form an air curtain around the passenger's face and successfully deflect the cough droplets towards the floor. Various simulations were carried out on aircraft cabins with single and dual-side vent configurations commonly seen in mixing ventilation systems. The droplets in the breathing zone of the passengers are measured in both ventilation systems and compared with the existing cabins to appreciate the merit of implementing the control device in aircraft cabins.