Computational fluid dynamics simulation of airborne COVID transmission in urban bus with different HVAC configurations

Abstract

The HVAC systems in closed buses promote high particle spread. Lagrangian particle tracking simulations were carried out to evaluate airborne COVID transmission through droplets emitted by sneezing while Eulerian simulations were performed to account for the spread of aerosols emitted by breathing. The position of passengers as well as the effect of three HVAC configurations were evaluated. On one hand, it was concluded that large droplets can travel more than 3 m without being significantly affected by the inflow conditions, but small droplets are easily dispersed by the airflow, and many of them are captured by the HVAC systems. On the other hand, the HVAC systems quickly spreads aerosols along the whole of the bus, increasing the average risk for all passengers, but sensibly reducing the high local risks observed under motionless inflow conditions. The transmission risk was calculated by applying the Wells-Riley model, concluding that the transmission risk for a 20-min trip could remain below 0.5% if HVAC configurations with many inlet/outlet vents are implemented, and the passengers remain in silence and wear face masks.

A numerical investigation on indoor air ventilation design and aerosol transportation: a case study in a hospital hall

“…However, in real-world scenarios, if all individuals wear masks, the infection rate is expected to be even lower. 21 In summary, existing studies have addressed the various aspects of COVID-19 control measures, with a specific focus on aerosol transmission and the influence of indoor air quality. However, there are still knowledge gaps regarding aerosol transportation in large spaces and the design of airflow organization to mitigate virus transmission in these environments.…”

“…However, in real-world scenarios, if all individuals wear masks, the infection rate is expected to be even lower. 21…”