Abstract View
Dynamics of Size Distribution Evolution of Human Expelled COVID-19 Droplets for Coughing and Speaking: A Simulation Study
JOSHIN KUMAR, Yang Wang, Benjamin Sumlin, Esther Monroe, Nishit Shetty, Rajan K. Chakrabarty, Washington University in St. Louis
Abstract Number: 503
Working Group: Infectious Aerosols in the Age of COVID-19
Abstract
The dynamics of the size distribution of virus-containing human expelled droplets is significant because it determines the deposition pattern in the human respiratory system, the lifetime of droplets in the indoor and outdoor spaces, and consequently, the transmission of respiratory diseases such as COVID-19.
Recent experimental studies have produced data on the initial size distribution for various expiratory activities. This initial size is often used directly for lifetime calculations which underestimates the lifetime of droplets. Hence, we must account for the size dynamics of droplets containing the COVID-19 virus to produce more realistic results.
Here, we present the results of a simulation study on the size distribution evolution of expelled droplets as reported by Prof. Lidia Morawska’s group in previous publications. In our model formulation, we have accounted for the environmental parameters such as evaporation, relative humidity, and room temperature while establishing and solving non-linear coupled differential equations for heat and mass transfer across the droplet and environment.
We show that considering the heat and mass transfer, the virus-containing human expelled droplets tend to shrink to smaller sizes, allowing them to stay unsettled in undisturbed indoor spaces for as long as a week. Also, modeling the dynamics enables us to see the transition states of size distribution as the droplets undergo evaporation and shrink to steady-state sizes within the order of ~0.1 seconds.