Transport of Airborne Particles from an Unobstructed Cough Jet

Liu, Shichao; Novoselac, Atila

doi:10.1080/02786826.2014.968655

Cited by 33 publications

(36 citation statements)

References 35 publications

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“…A number of other studies examined different particle sizes, but they mostly had no conclusion on the influence of particle size on the risk of cross‐infection. Liu and Novoselac analyzed the spread behavior of 3 particle sizes (0.77, 2.5, and 7.0 μm) generated from a cough and reported that the larger particles have a lower concentration in the vicinity of the receiver occupant in front. However, they used only very simplified dummies at a fixed separation distance of 1.2 m. Further studies are required.…”

Section: Current Understanding Of Airborne Transmission Indoorsmentioning

confidence: 99%

Airborne spread of expiratory droplet nuclei between the occupants of indoor environments: A review

2018

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This article reviews past studies of airborne transmission between occupants in indoor environments, focusing on the spread of expiratory droplet nuclei from mouth/nose to mouth/nose for non-specific diseases. Special attention is paid to summarizing what is known about the influential factors, the inappropriate simplifications of the thermofluid boundary conditions of thermal manikins, the challenges facing the available experimental techniques, and the limitations of available evaluation methods. Secondary issues are highlighted, and some new ways to improve our understanding of airborne transmission indoors are provided. The characteristics of airborne spread of expiratory droplet nuclei between occupants, which are influenced correlatively by both environmental and personal factors, were widely revealed under steady-state conditions. Owing to the different boundary conditions used, some inconsistent findings on specific influential factors have been published. The available instrumentation was too slow to provide accurate concentration profiles for time-dependent evaluations of events with obvious time characteristics, while computational fluid dynamics (CFD) studies were mainly performed in the framework of inherently steady Reynolds-averaged Navier-Stokes modeling. Future research needs in 3 areas are identified: the importance of the direction of indoor airflow patterns, the dynamics of airborne transmission, and the application of CFD simulations.

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Section: Current Understanding Of Airborne Transmission Indoorsmentioning

confidence: 99%

Airborne spread of expiratory droplet nuclei between the occupants of indoor environments: A review

2018

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“…Classic fluid mechanics theories on starting and interrupted jets [22, 28–30] provide insights into cough flow development. Hypothetically, these theories can be easily extended to cough flows [31]. However, the existing studies have only dealt with simple temporal exit velocity, such as the pulsation profile, whereas a real cough exhibits a more complex temporal velocity profile approximated as a combination of gamma-probability-distribution functions [15] (see Fig 1A).…”

Section: Introductionmentioning

confidence: 99%

Human Cough as a Two-Stage Jet and Its Role in Particle Transport

Wei

2017

PLoS ONE

134

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The human cough is a significant vector in the transmission of respiratory diseases in indoor environments. The cough flow is characterized as a two-stage jet; specifically, the starting jet (when the cough starts and flow is released) and interrupted jet (after the source supply is terminated). During the starting-jet stage, the flow rate is a function of time; three temporal profiles of the exit velocity (pulsation, sinusoidal and real-cough) were investigated in this study, and our results showed that the cough flow’s maximum penetration distance was in the range of a 50.6–85.5 opening diameter (D) under our experimental conditions. The real-cough and sinusoidal cases exhibited greater penetration ability than the pulsation cases under the same characteristic Reynolds number (Rec) and normalized cough expired volume (Q/AD, with Q as the cough expired volume and A as the opening area). However, the effects of Rec and Q/AD on the maximum penetration distances proved to be more significant; larger values of Rec and Q/AD reflected cough flows with greater penetration distances. A protocol was developed to scale the particle experiments between the prototype in air, and the model in water. The water tank experiments revealed that although medium and large particles deposit readily, their maximum spread distance is similar to that of small particles. Moreover, the leading vortex plays an important role in enhancing particle transport.

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“…Accordingly, the cough velocity was varied in the range of [6 m/s; 22 m/s] in this study. Furthermore, Gupta et al [34] found that the average mouth opening for males during a cough is equal to 4 cm 2 which was used in several cough studies [37,38]. Therefore, this value was adopted in the current work corresponding to an equivalent mouth diameter of nearly 2.25 cm.…”

Section: Characterization Of Exhaled Jetsmentioning

confidence: 99%

Transient transport model of particles resulting from high momentum respiratory activities: Inter-personal exposure

Habchi

Ghali

Ghaddar

2015

Building and Environment

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a b s t r a c tIn this work, a transient mathematical multi-region zonal transport model of particle behavior resulting from high momentum respiratory activities (HMRA) is developed focusing on the transient interpersonal exposure (IPE) in indoor spaces ventilated by displacement ventilation (DV) systems. The developed model was validated by experimentation and by published empirical data.Three stages are identified with respect to time for the variation of the IPE: a first stage dominated by the propagation and decay of the exhaled jet, a particles' redistribution stage, and a particles' removal stage. The inhaled dose is affected by the DV flow rate, cough velocity, particle diameter and distance between the occupants. The DV system with a flow rate of 100 L/s reduced significantly the inhaled dose during particle redistribution and removal stages decreasing the total inhaled dose by 83% compared to a flow rate of 50 L/s. IPE is higher when particle diameter is increased from 1 to 20 mm due to the opposition of particle removal by the upward DV.A comparison between steady and transient modeling of the IPE showed that steady modeling captures the physics affecting particle spread due to HMRA but it over-predicts the inhaled dose. It is found that for a DV flow rate of 100 L/s and a cough velocity of 22 m/s during 1 s, and 1 mm particles, the minimum required distance between the occupants for a threshold inhaled dose of 10 À5 kg is nearly 0.5 m by transient modeling while it is 2.15 m by steady state modeling.

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Transport of Airborne Particles from an Unobstructed Cough Jet

Cited by 33 publications

References 35 publications

Airborne spread of expiratory droplet nuclei between the occupants of indoor environments: A review

Airborne spread of expiratory droplet nuclei between the occupants of indoor environments: A review

Human Cough as a Two-Stage Jet and Its Role in Particle Transport

Transient transport model of particles resulting from high momentum respiratory activities: Inter-personal exposure

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