  Transmission of highly infectious respiratory diseases, including SARS-CoV-2
are facilitated by the transport of tiny droplets and aerosols (harboring
viruses, bacteria, etc.) that are breathed out by individuals and can remain
suspended in air for extended periods of time in confined environments. A
passenger car cabin represents one such situation in which there exists an
elevated risk of pathogen transmission. Here we present results from numerical
simulations of the potential routes of airborne transmission within a model car
geometry, for a variety of ventilation configurations representing different
combinations of open and closed windows. We estimate relative concentrations
and residence times of a non-interacting, passive scalar -- a proxy for
infectious pathogenic particles -- that are advected and diffused by the
turbulent airflows inside the cabin. Our findings reveal that creating an
airflow pattern that travels across the cabin, entering and existing farthest
from the occupants can potentially reduce the transmission.
