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

Abstract

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. In this paper, the transport of the SARS-CoV-2 virus through human respiratory particles is examined using transient Computational Fluid Dynamics (CFD) simulations to determine the impacts different ventilation configurations 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 proprietary Navier-Stokes finite-volume solver, RavenCFD by Corvid Technologies, and then using Lagrangian particle tracking (LPT) post processing techniques. The LPT methods used allowed for the injection of respiratory particles, according to distributions found in literature, which included sneezing, coughing, and speaking. To fully investigate the problem space the moving bus was modeled with the windows in various states of closure and with various HVAC configurations. In all scenarios, a volumetric Viral Mean Exposure Time (VMET), which considers the viral load calculations, was used to quantify the various exposure risk of all passengers on the bus. It was found that the most efficient ventilation system on a public transport bus was to keep the windows closed and HVAC of main cabin at maximum to minimize the viral exposure within the bus.