| NSF Org: |
CBET Division of Chemical, Bioengineering, Environmental, and Transport Systems |
| Recipient: |
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| Initial Amendment Date: | April 14, 2020 |
| Latest Amendment Date: | April 14, 2020 |
| Award Number: | 2029370 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Ron Joslin
rjoslin@nsf.gov (703)292-7030 CBET Division of Chemical, Bioengineering, Environmental, and Transport Systems ENG Directorate for Engineering |
| Start Date: | May 1, 2020 |
| End Date: | August 31, 2021 (Estimated) |
| Total Intended Award Amount: | $200,000.00 |
| Total Awarded Amount to Date: | $200,000.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
1 NASSAU HALL PRINCETON NJ US 08544-2001 (609)258-3090 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
NJ US 08544-2020 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | COVID-19 Research |
| Primary Program Source: |
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| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.041 |
ABSTRACT
Aerosol transport of viruses during breathing and speaking, as is common during social interactions of people, is largely unstudied. There is significant recent evidence that the fluid dynamics behind these flows may play a significant role in the spread of Covid-19. The rapid spread of Covid-19 highlights the lack of effective guidelines and mitigation strategies for reducing the impact of a contagious virus in the absence of a vaccine. Recent evidence from hospitals, and even the press, suggests that the fluid dynamics of this transport pathway should be re-investigated. The focus of this research will be to quantify the complex flows associated with speech and breathing during a conversation or nearby encounter and show how transmission of particles between individuals occurs. The understanding gained from this work will provide actionable mitigation strategies to reduce transmission from asymptomatic people. These outcomes can be useful in the short term by offering routes to reducing potential viral transport and future infections.
This research will show how the inherent structural flow difference between exhalation and inhalation during speech or simple breathing could be a potent yet unsuspected transport mechanism for pathogen transmission. The results will quantify an important aspect of this transmission, which in the case of Covid-19 is associated with asymptomatic carriers during relatively close social interactions. The quantitative characterization of this important topic surrounding viral transmission has largely been absent from the fluid mechanics and transport phenomena literatures, and even absent more generally from quantitative studies of public health. Using flow visualization and numerical simulations, the investigation will decipher the fluid dynamics in the neighborhood of the head of an individual during breathing and speaking, and the corresponding environmental mixing important to potential transmission (inhalation of particles by a nearby person). This approach will allow quantifying the fraction of particles exhaled by one person that are inhaled by a nearby person as a function of their separation distance. In these ways, the research will shed new light on a simple yet fundamental mechanism of transport associated with simple human activities, i.e., breathing and speaking, which can be generalized to many pathogens and aid in the identification of potential mitigation strategies for disease transmission by aerosols.
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.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
Many scientific reports document that asymptomatic and
presymptomatic individuals contribute to the spread of COVID-19,
at least in part during conversations in social interactions. Indeed, current public health measures focused on ventilation seek to maintain as much fresh air in spaces as possible. Droplet emission
occurs during speech, yet few studies document the air flows accompanying speech that carry small aerosol droplets from an infected individual to a susceptible individual, i.e., the transport mechanism is poorly documented and poorly understood. This lack of understanding prevents informed public health guidance for risk reduction and mitigation strategies. Our research focused on analyzing the air flows during breathing and speaking, i.e., ordinary conversations, ncluding phonetic features, using orders-of-magnitude estimates, numerical simulations, and laboratory experiments. We document the spatiotemporal structure of the expelled airflow, e.g., how far does the exhaled air propagate and how does the concentration of exhaled particles change with distance from the speaker. We document that phonetic characteristics of plosive sounds like “P” lead to enhanced directed transport, including jet-like flows that entrain the surrounding air. With these quantitative features understood we modeled the risk in certain situations accounting for both the separation distance (social distance) and contact time. We also began to study the corresponding air flows when individuals are masked; many studies document the important filtration features of masks so again our focus was on the resulting air flows that carry any droplets released from a speaker. Finally, we began to study air flows produced by professional musicians during performances in a collaboration with the MET Orchestra Musicians in New York City.
Last Modified: 10/03/2021
Modified by: Howard A Stone
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