Transport of Droplets Expelled by Coughing in Ventilated Rooms

Abstract

This study aims to understand the transport and dispersal of droplets produced by coughing in a ventilated room. Experiments were conducted to measure the initial velocity and the duration of a coughing burst. Computational fluid dynamics with a Eulerian—Lagrangian model was used to investigate the transport characteristics of evaporating droplets expelled into the ventilated room. The simulation results indicate that if expelled horizontally the droplets finally settle if their initial size is >100 μm, while if expelled upwards the droplets only settle if their initial size is ≥300 μm. Different ventilation set-ups vary in their ability to remove droplets produced by coughing. The mixing ventilation system has an almost equal efficiency for removing small passive droplets and the nuclei of droplets whose original size was 100 and 80 μm, respectively. For displacement ventilation, although it has high efficiency in removing small passive droplets, it has difficulty in removing the nuclei of large droplets. In the displacement system, small droplets show a two-zonal distribution in the room, but the nuclei of large droplets are subjected to gravitational force and tend to settle in the lower part of the room.