Computational Fluid Dynamics Simulation of Inter-Vehicle Ventilation Systems: A New Design Approach

The outbreak of COVID-19 pandemic in the beginning of 2020 has made it necessary to review many practices in countless areas, changing our lifestyles drastically. Humanity has put health issues in priority to deal with the disease effectively. While health systems are having difficult times in terms of patient care, vaccination, and treatment protocols, existing designs in many areas have proven to be inefficient in preventing or decelerating the pandemic. As the disease is transmitted mainly by particle transfer through coughing, sneezing, and even with speaking, wearing face masks and keeping a distance of 2 m as well as hygiene (especially hand) are shown to be effective methods. However, long exposure to indoor air populated with people is still a major risk due to the possibility of high concentration of virus-contaminated air. Ventilation systems in general must be redesigned, not only in terms of filtering capabilities, but reestablishing the air streams taking place during the ventilation as well. In modern buses as well as passenger aircrafts, ventilation air is blown from a narrow outlet/diffuser to guarantee a laminar flow for passenger comfort. The air is then returned to the central ventilation system through a large grille that is mostly located in the rear part of the bus. The objective of this numerical study is to visualize the air streams within a bus due to ventilation. Examining the flow visualization shows that the exhaled air from the infected passengers in the front seats can easily be conveyed along the bus, making it possible to be inhaled by healthy persons in other seats, posing a high health risk. Therefore, it is suggested that the air not be returned to the central ventilation system through a rear grille, but instead longitudinal grilles parallel to supply outlets providing a stream perpendicular to longitudinal axis of bus, thus reducing the risk of contaminated air being inhaled by other passengers.