Abstract
In this paper, we investigate the aerosol cloud flow physics during three respiratory actions by humans (such as coughing, talking, and breathing). With given variables (i.e., velocity, duration, particle size and number of particles, and ambient conditions), the standoff safe distance during coughing, talking, and breathing should be the distance where virus-laden droplets and aerosols do not have significant transmission to another person. However, at a critical distance, the aerosol cloud flux can still be extremely high, which can immediately raise the transmission in a localized area to another person during a static condition. In this study, computational fluid dynamics analysis of selective respiratory actions has been carried out to investigate the effect of the standoff distance and assess the importance of social distancing in indoor places. The prediction of the aerosol transport due to flow generated from coughing, talking, and breathing was obtained by applying the Eulerian–Lagrangian approach. From the simulation results, it can be concluded that the aerosols released due to continuous talking travel a similar distance to that released due to sudden coughing. On the other hand, aerosols exhaled from breathing do not travel a long distance but float in air for a long time.
Highlights
Droplets ejected from an asymptomatic host are one of the biggest risks during the current coronavirus (COVID-19) pandemic in the transmission of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)
Stringent measures such as lockdown have reduced the spread of the virus and the public places are gradually opening, social distancing will be followed for the foreseeable future and the risks of transmission will not be reduced until a large section of population is vaccinated
The transport of aerosol has been simulated using 10, 5, and 1 μm droplets, and it was assumed that the aerosol was generated at the source. (Vuorinen et al, 2020) explained that the actual resolution of the initial event is not critically important for simulating aerosol transport as the spreading and dissipation of aerosol occur over a much longer time scale compared to the initial expiratory events
Summary
Droplets ejected from an asymptomatic host are one of the biggest risks during the current coronavirus (COVID-19) pandemic in the transmission of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Stringent measures such as lockdown have reduced the spread of the virus and the public places are gradually opening, social distancing will be followed for the foreseeable future and the risks of transmission will not be reduced until a large section of population is vaccinated. Experimental or numerical modeling of the flow dynamics of droplets and aerosols transport from expiratory flows will provide the quantitative data for developing guidelines for social distancing in various indoor and outdoor settings. As advised through fundamental assessments based on fluid dynamics (Mittal et al, 2020), the COVID-19 pandemic has pushed the scientific community and attracted new studies to be undertaken to understand critical scientific challenges, such as respiratory droplet formation, two-phase expiratory flows, droplet evaporation and transport, and associated aerodynamics [Feng et al (2020) and Xu et al (2017)]
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