Effects of slope and speed of escalator on the dispersion of cough-generated droplets from a passenger

Abstract

During the pandemic of COVID-19, the public is encouraged to take stairs or escalators instead of elevators. However, the dispersion of respiratory droplets in these places, featured by slopes and human motion, is not well understood yet. It is consequently unclear whether the commonly recommended social-distancing guidelines are still appropriate in these scenarios. In this work, we analyze the dispersion of cough-generated droplets from a passenger riding an escalator with numerical simulations, focusing on the effects of the slope and speed of the escalator on the droplet dispersion. In the simulations, a one-way coupled Eulerian–Lagrangian approach is adopted, with the air-flow solved using the Reynolds-averaged Navier–Stokes method and the droplets modeled as passive Lagrangian particles. It is found that the slope alters the vertical concentration of the droplets in the passenger's wake significantly. The deflection of cough-generated jet and the wake flow behind the passenger drive the cough-generated droplets upwards when descending an escalator and downwards when ascending, resulting in both higher suspension height and larger spreading range of the viral droplets on a descending escalator than on an ascending one. These findings suggest that the present social-distancing guidelines may be inadequate on descending escalators and need further investigation.

Computational decision-support tools for urban design to improve resilience against COVID-19 and other infectious diseases: A systematic review

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Airborne transmission of COVID‐19 virus in enclosed spaces: An overview of research methods

“…Liu et al104 investigated airborne particle exposure in elevators. Li et al105 used theLagrangian method to evaluate the impact of the speed, slope, and direction of an escalator on the spread of droplets. All these studies indicated that the Lagrangian model could be used to assess the risk of exposure to airborne particles.The Eulerian and Lagrangian models are usually coupled with numerical calculations of the flow field.…”

Numerical model for cough‐generated droplet dispersion on moving escalator with multiple passengers

“…Also, only a single passenger was included for risk evaluation of infectious droplets and the interaction with other passengers was ignored in the previous studies. 20,21 In this paper, we investigate the effect of cough-generated droplets expelled from an infected person on other passengers riding the same escalator. A geometrically detailed escalator model is used with steps and handrails moving in ascending and descending directions.…”