Multiphase Modelling and Experimental Characterization of Respiratory Microdroplet Suspension and Resuspension Dynamics Near Surfaces

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The main transmission routes for COVID-19 are respiratory droplets and close contact. Understanding environmental spreading pathways of COVID-19 is critical for improving safety practices. Although the flow physics of respiratory droplets at large length scales has been the focus of many studies, the microscale dynamics of the suspension behavior of individual respiratory droplets on common personal protective equipment (PPE) surfaces and the secondary exposure risk due to resuspension of those droplets have not been systematically evaluated. Initial studies show that environmental conditions such as humidity and temperature as well as surface properties, e.g. surface chemistry, roughness and wettability have significant effects on the evolution mechanism of aerosols and droplets. In particular, there is no comprehensive study on how temperature and humidity influence the aerodynamics and surface interaction of aerosols. The goal of this project is to provide fundamental understanding of the interaction between individual respiratory microdroplets and PPE surfaces under external disturbance such as body motion, through combined computational modeling and experiments. This research will help explore potential approaches that can be practiced by medical staff and general public to control motion, humidity, temperature, and surface modification that reduces aerosol-based virus spreading. The project will also incorporate research into education of undergraduate and graduate students in class, making a droplet-surface simulation tool to be made available to the research community, and outreach to K-12 and minority students.The goal of this project is to provide both a fundamental understanding of thermal-humidity-temporal microdroplet dynamics and a prediction tool for microdroplet surface interaction. The specific aims of the proposal work are to: (i) Develop a 3D multi-phase computational model for evaporation, transport, suspension, adhesion, and resuspension dynamics of respiratory droplet on various surfaces; (ii) Generate individual mimetic-virus laden respiratory microdroplets, with chemical composition and sizes similar to respiratory droplets, and investigate systematically the dynamics of the suspension and resuspension behavior of these droplets near various surfaces in a controlled environment; and (iii) Explore the effects of temperature, humidity, surface properties, and external disturbance on the suspension and resuspension behavior of droplets and suggest potential approaches for minimizing the aerosol spreading of virus. The integrated computational and experimental approach will create comprehensive understanding of the droplet-based virus transport and evolution as a function of humidity, temperature and surface characteristics.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.