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

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 modeled as passive Lagrangian particles. Simulation results show that the cloud of droplets locates around and below the waist height of the manikin after 2 s 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.

A computational study of expiratory particle transport and vortex dynamics during breathing with and without face masks

“…5,6 Researchers have sought to examine the scientific underpinning of these guidelines by investigating the underlying physics of respiratory events and transport mechanisms that contribute to the propagation of pathogen-carrying saliva droplets. 6–23 For example, Yang and co-workers 7,8 used a one-way Eulerian–Lagrangian framework to investigate saliva particle transport from a moving person in various situations. Bourouiba et al (2014), 20 and more recently, Leung et al (2020), 17 Fischer et al (2020), 18 and Verma et al (2020) 19 investigated experimentally indoor coughing and sneezing expiratory events and reported that saliva particles of such events could, under certain conditions, propagate as far as 7–8 m away from the person.…”

Analysis of the Airflow Generated by Human Activity Using a Mobile Slipstream Measuring Device

“…Droplet dispersion during coughing by people who are walking plays an important role in the transmission of COVID-19. A simulation showed that droplets in the air in a narrow space, such as a hallway, were transmitted below waist height (of the emitter) [28]. Wake measurements confirmed that the speed and distribution stabilized as the distance from the mobile slipstream at chest and waist height increased.…”

A smart mask for active defense against airborne pathogens

“…Such aerosol clouds include various types of cells (e.g., epithelial cells and leukocytes), ions present in mucus and saliva (e.g., Na , K , and Cl−), and, potentially, various infectious agents suspended in the droplets (e.g., bacteria, fungi, and viruses). Even weak air currents caused by innocuous daily activities, such as walking 7 or opening doors, can transport these infectious droplets over long distances ( ). Such airborne transmission is the primary driver for virus spread in indoor spaces such as bathrooms, doctor’s offices, daycare centers, and public transportation; it is also important in many outdoor environments 8 .…”