Session: 03-02-02 Bio-Inspired and Biomedical Fluid Mechanics

Paper Number: 87739

87739 - Interactions of Aerosol Droplets With Ventilated Airflows in the Context of Airborne Pathogen Transmission 

In previous research, it was determined that ample ventilation of an indoor space is one of the best methods to prevent the spread of COVID-19, along with the use of air purifiers and face coverings such as masks. The moving air in a ventilated space was shown to aid in dissipating the cloud of aerosols created through talking, coughing, sneezing, and other common processes of aerosol emission. This ventilation also occurs naturally through wind and similar phenomena in an outdoor setting, and is a large factor as to why pathogen transmission is far more common in unventilated enclosed spaces. The droplet dynamics of aerosols coming into contact with these ventilated crossflows were studied through experimental mapping of droplet displacement using an Aerodynamic Particle Sizer (APS), as well as through Computational Fluid Dynamics (CFD) simulations through Star CCM+. Additionally, large uniform airflows were simulated through CFD to analyze the impact of phenomena such as wind on aerosol droplets in outdoor settings. Through these experimental and simulated methods, the quantitative impact of crossflow ventilation on droplet dynamics can be determined.

The experimental testing utilizes a uniform crossflow over a subject, who through talking, coughing, and sneezing, emits aerosol droplets that are read downstream utilizing modern aerosol measuring equipment at various locations for repeated scenarios. These tests were additionally repeated five times at each location to average results and approximate droplet ambience, which was removed from the final results. Through simulation the same scenarios were performed with the additional case of an outdoor setting with an airflow akin to wind. Modeled using a hybrid Eulerian-Lagrangian approach with a Detached Eddy Simulation model to account for the turbulent nature of respiratory-induced flow and ventilation, the CFD simulation tracks the droplet’s thermal properties, as well as displacements associated with lift, drag, pressure, and buoyancy.

The experimental and simulated data shows creating a disruption in a droplet’s initial pathing through ventilated airflows can greatly reduce the initial density of airborne droplets within a 100-centimeter squared test area 1 meter along the flight vector by around 90%. Additionally, a strong enough airflow has the potential to reduce the total linear distance the droplets travel by half, and can prevent droplets from settling on commonly used surfaces such as desks and keyboards. These results quantitatively confirm the effectiveness of ventilated crossflows both indoors and outdoors, and while the possibility of transmitting airborne pathogens is not completely nullified, it is drastically reduced.

Presenting Author: Steven Schroeder University of Central Florida