Abstract
COVID-19 pandemic has strikingly demonstrated how important it is to develop fundamental knowledge related to generation, transport and inhalation of pathogen-laden droplets and their subsequent possible fate as airborne particles, or aerosols, in the context of human to human transmission. It is also increasingly clear that airborne transmission is an important contributor to rapid spreading of the disease. In this paper, we discuss the processes of droplet generation by exhalation, their potential transformation into airborne particles by evaporation, transport over long distances by the exhaled puff and by ambient air turbulence, and final inhalation by the receiving host as interconnected multiphase flow processes. A simple model for the time evolution of droplet/aerosol concentration is presented based on a theoretical analysis of the relevant physical processes. The modeling framework along with detailed experiments and simulations can be used to study a wide variety of scenarios involving breathing, talking, coughing and sneezing and in a number of environmental conditions, as humid or dry atmosphere, confined or open environment. Although a number of questions remain open on the physics of evaporation and coupling with persistence of the virus, it is clear that with a more reliable understanding of the underlying flow physics of virus transmission one can set the foundation for an improved methodology in designing case-specific social distancing and infection control guidelines.
Competing Interest Statement
The authors have declared no competing interest.
Funding Statement
SB acknowledges support from the Office of Naval Research (ONR) as part of the Multidisciplinary University Research Initiatives (MURI) Program, under grant number N00014-16-1-2617 and from the UF Informatics Institute. SZ wishes to thank the French ANR for its support through its flash Covid-19 program - NANODROP grant, the ERS Advanced Grant TRUFLOW and the PRACE network for its Covid-19 Fast Track Call grant NANODROP on the Irene TGCC. AS acknowledges funding from the PRIN project Advanced computations and experiments in turbulent multiphase flow (Project No. 2017RSH3JY). GA acknowledges support through the NSF Grant No. CBET 2029548 and the Clarkson IGNITE Fellowship. LB acknowledges support from the Smith Family Foundation, the Massachusetts Institute of Technology (MIT) Policy Lab, the MIT Reed Fund, and the Esther and Harold E. Edgerton Career Development chair at MIT.
Author Declarations
I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.
Yes
The details of the IRB/oversight body that provided approval or exemption for the research described are given below:
University of Florida
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Yes
Data Availability
The paper is theoretical and self contained. The curated data from the additional simulations being performed is available at the attached link.
https://uflorida-my.sharepoint.com/personal/josalinas_ufl_edu