Modeling Transport of SARS-CoV-2 Inside a Charlotte Area Transit System (CATS) Bus

TL;DR

This study models the airflow and respiratory particle transport inside a CATS bus to evaluate intervention strategies for reducing SARS-CoV-2 exposure risk using advanced CFD simulations and particle tracking.

Contribution

It introduces a detailed CFD-based model of respiratory particle transport in a bus environment to assess intervention effectiveness against COVID-19.

Findings

Open windows reduce viral exposure time

HVAC settings significantly impact particle removal

Simulation identifies effective ventilation strategies

Abstract

We present in this paper a model of the transport of human respiratory particles on a Charlotte Area Transit System (CATS) bus to examine the efficacy of interventions to limit exposure to SARS-CoV-2, the virus that causes COVID-19. The methods discussed here utilize a commercial Navier-Stokes flow solver, RavenCFD, run using a massively parallel supercomputer to model the flow of air through the bus under varying conditions, such as windows being open or the HVAC flow settings. Lagrangian particles are injected into the RavenCFD predicted flow fields to simulate the respiratory droplets from speaking, coughing, or sneezing. These particles are then traced over time and space until they interact with a surface or are removed via the HVAC system. Finally, a volumetric Viral Mean Exposure Time (VMET) is computed to quantify the risk of exposure to the SARS-CoV-2 under various environmental and occupancy scenarios. Comparing the VMET under varying conditions should help identify viable methods to reduce the risk of viral exposure of CATS bus passengers during the COVID-19 pandemic.