Modeling the transmission of infectious aerosols

Inhalation of micron-sized droplets represents the dominant transmission mechanism for influenza and rhinovirus, and recent research shows that it is likely also the case for the novel coronavirus.  Increasing evidence suggests that the transmission of infectious aerosols is more complex than previously thought. Coughing, sneezing and even talking yield a gaseous flow field near the infected person that is dynamic and turbulent in nature. Existing models commonly employed in simulations of aerosol transmission attempt to represent the effect of turbulence using random walk models that are often phenomenological in nature, employing adjustable parameters and inherently assuming the turbulent fluctuations ‘felt’ by a droplet do not depend upon direction. To design physics-informed guidelines to minimize the spread of this virus, improved predictive modeling capabilities for effectively tracking the aerosol paths are needed. Dr. Aaron M. Lattanzi and Prof. Jesse Capecelatro, from Mechanical Engineering and MICDE are tackling this problem by focusing on mathematical modeling of aerosol dispersion. They derived analytical solutions for the mean-squared-displacement resulting from systems of stochastic differential equations. A key element of their methodology is that the solution connects stochastic theory inputs to statistics present in high-fidelity simulations or experiments, providing a framework for developing improved models.

Simple simulation of aerosol dispersion from a single-point source. The grey, cone-like surface is the approximation using Force Langevin (FL) theory and the colored particles are from integration of Newton’s equations with stochastic drag forces.

Prof. Capecelatro’s research group develops physics-based models and numerical algorithms to leverage supercomputers for prediction and optimization of the complex flows relevant to energy and the environment. The main focus of their research involves developing robust and scalable numerical tools to investigate the multiphysics and multiscale phenomena under various flow conditions, like those that they study here. They recently submitted their findings to the Journal of Fluid Mechanics, and are continuing to work on this problem hoping it will help understand the transmission of COVID-19 and therefore help optimize current guidelines.