Understanding Transmission Dynamics of COVID-19-Type Infections by Direct Numerical Simulations of Cough/Sneeze Flows

Diwan, Sourabh S.; Ravichandran, S.; Govindarajan, Rama; Narasimha, R.

doi:10.1007/s41403-020-00106-w

Cited by 58 publications

(58 citation statements)

References 14 publications

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“…Although Direct Numerical Simulations have been carried out in the past, 24 to our knowledge, this is the first time that details on the temporal evolution of puff centroid, entrainment coefficient, and front topology have been reported.…”

Section: Introductionmentioning

confidence: 99%

Direct numerical simulation of the turbulent flow generated during a violent expiratory event

et al. 2021

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A main route for SARS-CoV-2 (severe acute respiratory syndrome coronavirus) transmission involves airborne droplets and aerosols generated when a person talks, coughs, or sneezes. The residence time and spatial extent of these virus-laden aerosols are mainly controlled by their size and the ability of the background flow to disperse them. Therefore, a better understanding of the role played by the flow driven by respiratory events is key in estimating the ability of pathogen-laden particles to spread the infection. Here, we numerically investigate the hydrodynamics produced by a violent expiratory event resembling a mild cough. Coughs can be split into an initial jet stage during which air is expelled through mouth and a dissipative phase over which turbulence intensity decays as the puff penetrates the environment. Time-varying exhaled velocity and buoyancy due to temperature differences between the cough and the ambient air affect the overall flow dynamics. The direct numerical simulation (DNS) of an idealized isolated cough is used to characterize the jet/puff dynamics using the trajectory of the leading turbulent vortex ring and extract its topology by fitting an ellipsoid to the exhaled fluid contour. The three-dimensional structure of the simulated cough shows that the assumption of a spheroidal puff front fails to capture the observed ellipsoidal shape. Numerical results suggest that, although analytical models provide reasonable estimates of the distance traveled by the puff, trajectory predictions exhibit larger deviations from the DNS. The fully resolved hydrodynamics presented here can be used to inform new analytical models, leading to improved prediction of cough-induced pathogen-laden aerosol dispersion.

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Section: Introductionmentioning

confidence: 99%

Direct numerical simulation of the turbulent flow generated during a violent expiratory event

et al. 2021

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“…The importance of these couplings have indeed been recognized in simulations of other aerosols, such as in combustion [51]. Other attempts include simulations with continuum models [52, 53] or mathematical models [54, 55].…”

mentioning

confidence: 99%

Extended lifetime of respiratory droplets in a turbulent vapour puff and its implications on airborne disease transmission

Chong

Hori

et al. 2020

Preprint

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To mitigate the COVID-19 pandemic, it is key to slow down the spreading of the life-threatening coronavirus (SARS-CoV-2). This spreading mainly occurs through virus-laden droplets expelled at speaking, screaming, shouting, singing, coughing, sneezing, or even breathing [1-7]. To reduce infections through such respiratory droplets, authorities all over the world have introduced the so-called "2-meter distance rule" or "6-foot rule". However, there is increasing empirical evidence, e.g. through the analysis of super-spreading events [6, 8-11], that airborne transmission of the coronavirus over much larger distances plays a major role [1-3, 7, 12-15], with tremendous implications for the risk assessment of coronavirus transmission. It is key to better and fundamentally understand the environmental ambient conditions under which airborne transmission of the coronavirus is likely to occur, in order to be able to control and adapt them. Here we employ direct numerical simulations of a typical respiratory aerosol in a turbulent jet of the respiratory event within a Lagrangian-Eulerian approach [16-18] with 5000 droplets, coupled to the ambient velocity, temperature, and humidity fields to allow for exchange of mass and heat [19] and to realistically account for the droplet evaporation under different ambient conditions. We found that for an ambient relative humidity of 50% the lifetime of the smallest droplets of our study with initial diameter of 10 μm gets extended by a factor of more than 30 as compared to what is suggested by the classical picture of Wells [20, 21], due to collective effects during droplet evaporation and the role of the respiratory humidity [22], while the larger droplets basically behave ballistically. With increasing ambient relative humidity the extension of the lifetimes of the small droplets further increases and goes up to 150 times for 90% relative humidity, implying more than two meters advection range of the respiratory droplets within one second. Smaller droplets live even longer and travel further. Our results may explain why COVID-19 superspreading events can occur for large ambient relative humidity such as in cooled-down meat-processing plants [10] or in pubs with poor ventilation. We anticipate our tool and approach to be starting points for larger parameter studies and for optimizing ventilation and indoor humidity controlling concepts, which in the upcoming autumn and winter both will be key in mitigating the COVID-19 pandemic.

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“… Modeling and CFD simulation of turbulent flow, similar to expiratory flows, and analysis of temperature distribution in a moist plume. Temperature distribution in a “dry cough” simulation indicates that liquid content expelled in this situation spreads rapidly (< 1 s) along more than 1 m [36] . …”

Section: How Flow Physics Comprehension Can Enable Mitigation and Prementioning

confidence: 99%

How chemical engineers can contribute to fight the COVID-19

Santana

Souza

Lopes

et al. 2020

Journal of the Taiwan Institute of Chemical Engineers

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Highlights Vaccine development and medication used in medical protocols were described. The main fluid dynamic of transmission routes were elucidated. Successful applications of reverse engineering and 3D printing were reported. The state-of-art of Microfluidic-based chips in virus detection was detailed. The use of Artificial Intelligence on COVID-19 diagnostics was presented.

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Understanding Transmission Dynamics of COVID-19-Type Infections by Direct Numerical Simulations of Cough/Sneeze Flows

Cited by 58 publications

References 14 publications

Direct numerical simulation of the turbulent flow generated during a violent expiratory event

Direct numerical simulation of the turbulent flow generated during a violent expiratory event

Extended lifetime of respiratory droplets in a turbulent vapour puff and its implications on airborne disease transmission

How chemical engineers can contribute to fight the COVID-19

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