<p dir="ltr">With the current outbreak of SARS-CoV-2, public transportation is a key area which must be investigated to ensure both passenger safety and efficiency of passenger transport to best serve the community and reduce environmental footprint. Since conducting physical tests of a bus in a wind tunnel to obtain viral load measurements is impractical, CFD is a better alternative that provides us a much more detailed knowledge of the viral flow. In this paper, the transport of the SARS-CoV-2 virus through human respiratory particles is examined using CFD to determine the impacts of HVAC settings and having windows open/closed on the probability of viral exposure. The motion of the viral particles was simulated first by solving for the flow field inside the bus using a commercial Navier-Stokes solver, RavenCFD by Corvid Technologies, and then using Lagrangian particle tracking (LPT) post processing techniques. The quasi-transient simulations were run using the Shear Stress Transport (SST) turbulence model.&nbsp; The LPT methods used allowed for the injection of respiratory particles according to distributions found in literature. To fully investigate the problem space, not only was the moving bus modeled with the windows in various states of closure and with various HVAC configurations, but the passengers were also modeled with each having three possible viral injection events that include speaking, coughing, and sneezing. In all scenarios, a volumetric Viral Mean Exposure Time (VMET), which takes into account the viral load calculations, was used to quantify the various exposure risk of all passengers on the bus. The ventilation of the bus with open windows was identified in three different settings in this paper. The moving bus had windows opened while the doors were closed, with the first case having half of the bus windows opened, and the other two cases having two alternate open window setups. While the windows were open, the HVAC was set at two different settings of either maximum flow or entirely shut off.&nbsp; The seating configuration in this paper was taken in consideration with the local public transport bus’s Covid-19 restrictive settings, with only 14 passengers and a driver present in the bus at a given time. The Covid-19 restrictive bus designs also include transparent barriers between the seats, and they were also modeled for this study to provide a comprehensive particle flow study for the SARS-CoV-2 viral particles and determine the safest and most efficient ventilation system on a public transport bus.</p>

Effects of HVAC Settings and Windows Open or Close on the Sars-CoV-2 Virus Transmission Inside a Mass Transit System Bus

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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