Collaborative Research: Effect of Pulsatility on Expiratory Droplet-Laden Flows

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Predicting the dispersion of droplets and aerosols generated during expiratory events like sneezing, coughing, or speech is a key step towards understanding the spread of infectious diseases and to develop effective countermeasures to contain outbreaks. Existing open-source and commercial tools used in industry and academia, to predict dispersion of droplets and aerosols, rely on simplistic models that fail to capture details of the underlying turbulent flow physics. In this project, through a combined experimental and computational approach, advancements are made towards the development of improved models that could be easily embraced through direct implementation into existing tools. This project also encompasses significant education and outreach activities. The investigators will expand their ongoing efforts to adopt Virtual Reality based imaging to enable immersive three-dimensional representations of droplet-laden expiratory flow as an educational tool. These educational tools will be used for outreach events and workshops at both Auburn University and the University of Michigan.The overall goal of this collaborative experimental and computational project is to quantify the fundamental flow physics that govern the transport and dispersion of droplets in a pulsatile expiratory flow. Using an ex-vivo cough simulator and human subject experiments combined with direct numerical simulations we will quantify the role of flow interactions, generated by pulsatile expiratory flow, on aerosol dispersion and assess the penetration length of secondary expulsions. By combining time-resolved velocimetry with an extensively validated fluid-particle simulation methodology, this effort will break ground in uncovering new flow physics relating the influence of flow interactions on the entrainment and dispersion of droplets. Some of the anticipated outcomes include: (1) an extensive database of experimental measurements and high-resolution simulations; and (2) a sound theoretical foundation for modeling turbulent disperse two-phase flows. Such improved quantification of flow physics and development of reduced-order models will enable better prediction of droplet dispersion, a key step towards understanding the spread of viral infections. The methods developed will be used to study the interaction of droplet-laden expiratory jets with flow barriers (for example face shields) and evaluate their efficacy to mitigate the dispersion of impinging expiratory flows.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.