Violent respiratory diseases, i.e., coronavirus (COVID-19), spread through saliva in
coughs and sneezes or are even exhaled in the form of microbial pathogen micro-droplets.
Therefore, in this work, a comprehensive fully coupled Eulerian–Lagrangian method has been
applied for infection control, thus leading to a deeper understanding of the
saliva-disease-carrier droplet transmission mechanisms and also of their trajectory
tracking by using the OpenFOAM package. This model determines the droplet–air
interactions, the breakup process, and turbulent dispersion forces on each micro-droplet
that is expelled within the respiratory tract in a correct way. By examining a broad range
of initial velocities, size distributions, injection angles of saliva micro-droplets, and
mouth opening areas, we predict the maximum opening area that can be driven by
micro-droplets. One important contribution of this work is to present a correlation for
the length and width of the overall direct maximum reach of the micro-droplets, driven by
a wide range of mild coughs to intense sneezes. Our results indicate that the movement of
the expelled droplets is mainly influenced by their size, angle, velocity, and
environmental factors. During a virus crisis, like COVID-19, this paper can be used to
determine the “social distance” between individuals to avoid contamination, by inhaling or
touching their bodies, due to these saliva-disease-carrier droplets in sneezing, at
various social distance positions such as face-to-face, meeting standing, and near
equipment. The safe distance must be increased to around 4 m during a sneeze. By wearing a
face mask and by bending the head during a sneeze as a protective action, we can reduce
the contamination area to one-third and three-quarters, respectively. Furthermore, the
dispersion of the film of the expelled saliva micro-droplets and the spatial relationship
between the subjects, which affects the airflow inside the room, are also analyzed in
detail.