Effects of space sizes on the dispersion of cough-generated droplets from a walking person

TL;DR

This study models how cough droplets disperse behind walking individuals, revealing that space size influences dispersion modes and transmission risk, which is crucial for setting effective social distancing guidelines.

Contribution

It introduces a simulation approach combining RANS and Lagrangian particles to analyze droplet dispersion modes affected by space size during walking.

Findings

Droplets cluster around and below waist height within two seconds after coughing.

Two distinct dispersion modes are identified, each covering different contamination regions.

Small changes in space size can trigger a transition between dispersion modes.

Abstract

The dispersion of viral droplets plays a key role in the transmission of COVID-19. In this work, we analyze the dispersion of cough-generated droplets in the wake of a walking person for different space sizes. The air flow is simulated by solving the Reynolds-Averaged Navier-Stokes equations, and the droplets are modelled as passive Lagrangian particles. Simulation results show that the cloud of droplets locates around and below the waist height of the manikin after two seconds from coughing, which indicates that kids walking behind an infectious patient are exposed to higher transmission risk than adults. More importantly, two distinct droplet dispersion modes occupying significantly different contamination regions are discovered. A slight change of space size is found being able to trigger the transition of dispersion modes even though the flow patterns are still similar. This shows the importance of accurately simulating the air flow in predicting the dispersion of viral droplets and implies the necessity to set different safe-distancing guidelines for different environments.