Abstract
The precautionary measures recommended during the current COVID-19 pandemic do not consider the effect of turbulent airflow. We found the propagation of droplets and aerosols highly affected by this condition. The spread of respiratory droplets by the action of sneezing is characterized by the dynamics of two groups of droplets of different sizes: Larger droplets (300–900 μm) have a ballistic trajectory and can be spread up to 5 m, while a cloud of smaller droplets (100–200 μm) can be transported and dispersed at longer distances up to 18 m by the action of the turbulent airflow. In relation to the spread of exhaled aerosols during respiration, these remain in the air for long periods of time. In the presence of intense or moderate airflow, this set of particles follow airflow streamlines, and thus their propagation is directly determined by the air velocity field. Given the scientific evidence, these results should be considered in public debate about the aerodynamic dispersion characteristics of scenarios where social interactions occur and about the measures to mitigate the spread of the virus.
Highlights
David Heymann, from the London School of Hygiene and Tropical Medicine, who was one of the leaders during the SARS outbreak and is a public health expert, claimed on 20 February 2020 that the propagation of COVID-19 in open spaces was one of the important unknowns yet to be defined [1]
There are available studies aimed at analyzing the spread of respiratory droplets [17,18,19,20,21,22] and aerosols [23,24], up to our reach there is only one study that has attempted to estimate the effect of an airflow over the spread of respiratory droplets exhaled during a respiratory symptom [25]
In order to describe the aerodynamic dispersion of polydisperse respiratory droplets and aerosols exhaled during a sneeze and during simple breathing by a turbulent airflow, we implement a computational model using the framework of the commercial computational fluid dynamics (CFD) code ANSYS-FLUENT 18.2
Summary
David Heymann, from the London School of Hygiene and Tropical Medicine, who was one of the leaders during the SARS outbreak and is a public health expert, claimed on 20 February 2020 that the propagation of COVID-19 in open spaces was one of the important unknowns yet to be defined [1]. There are available studies aimed at analyzing the spread of respiratory droplets [17,18,19,20,21,22] and aerosols [23,24], up to our reach there is only one study that has attempted to estimate the effect of an airflow over the spread of respiratory droplets exhaled during a respiratory symptom [25] This situation would be applicable both to outdoor urban settings exposed to small-scale microclimatological wind and to indoor situations exposed to airflow caused by the natural or artificial ventilation of the space.
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