Study on atomization morphology of expelled respiratory liquids

Abstract

The outbreak of COVID-19 underscored the need for a better understanding of the fluid dynamics of disease transmission. Human respiratory activities such as coughing, sneezing, and even talking and eating expel a huge amount of pathogen-laden droplets, and during eating and drinking, the physical properties of saliva are changed. In this study, we investigate the atomization morphology of expelled saliva from the perspective of varying fluid physical properties. Using high-speed shadowgraph experiments on artificial saliva, we visualize and analyze the disintegration of viscoelastic liquid sheets into ligaments and droplets. We find that the viscosity and surface tension affect the droplet size formed from expelled saliva. We show that the changes in physical properties of saliva induced by eating and drinking favor the formation of smaller droplets, which drive the airborne transmission pathway of pathogens. Furthermore, we derive a theoretical model based on scaling arguments to explicate our experimental findings.