2020.08.24

Prediction and Countermeasures for Infection by Virus Contaminated Droplet in Indoor Environment

Research and Development by

Tsubokura Makoto, RIKEN Center for Computational Science / Kobe University

Corresponding Research Area

Indoor airflow simulation and visualization of droplets, which are necessary for improving the COVID-19 Infection Prevention Guidelines for each industrial sector


1. Air Flow Simulation - Effect by Face Mask and Face Shield

■Control effect on dispersion of droplet (substitute effect of face mask) is computed by super computer “Fugaku”

  • Catching effect, when coughing, can be expected if the droplet stays somewhere around 100 microns. On the other hand, catching effect on droplet less than 20 microns is low.
  • In case of using face shields as substitute for face masks to protect against droplet dispersion, the combined use of measures against small droplet such as ventilation has to be taken.
  • Henceforth, we will consider feasibility to substitute, when in need to take off face masks at times like eating and drinking, with things such as face shields and optimization of the design of them.

non-woven fabric mask 

Face shield

Courtesy of RIKEN, Toyohashi University of Technology and Kobe University, incorporation with Kyoto Institute of Technology and University of Osaka

1. Air Flow Simulation – Dispersion of Droplet in Restaurants①

■Situations of dispersion of droplet in restaurants, being in many infected cases during eating and drinking are computed by super computer “Fugaku”

  • Examined affect on droplet dispersion by humidity level in the room.
  • When humidity is high, most of droplet over 10 microns falls onto the desk and only small aerosol in less than several microns reaches the person in front of him. On the contrary, when humidity is low, droplet evaporates fast and get microminiaturized and the number of it falling down decreases largely, but the number of aerosol increases dispersing in the air.
  • Henceforth, we plan to consider further situations of restaurants such as influence by man-to-man distance and air from air conditioners.

Humidity 30%

Humidity 90%

Courtesy of RIKEN and Toyohashi University of Technology,in corporation with Kyoto Institute of Technology and University of Osaka

1. Air Flow Simulation – Dispersion of Droplet in Restaurants②

■Situations of dispersion of droplet in restaurants, being in many infected cases during eating and drinking are computed by super computer “Fugaku”

Partition height is the height from the floor. Mouth location is 1.15 m from the floor. Desk height is 0.75 m.

  • Assuming to cough without wearing masks
  • Can reduce aerosol droplet over persons 1.9 meters away to less than one-tenth by putting a 1.2-meter high partition.
  • Aerosol is found to reach to the opposite in 30 seconds or so with 1.2-meter high partition,but with 1.4-meter one it can be blocked almost fully.
  • It was found that there was no difference of effect made between height of 1.4 meters and 1.6.

No partition

1.4m high partition

1.2m high partition

1.6m high partition

Courtesy of RIKEN and Toyohashi University of Technology, in corporation with Kyoto Institute of Technology and University of Osaka

1. Air Flow Simulation - Aerosol Emission Effect by Window Opening in Commuting Trains

■Aerosol emission situation by ventilation in commuting trains of Yamate Line is computed by super computer “Fugaku”

  • Ventilation was started in virtual status of air inside being contaminated(cleaner in more blue than red).
  • Compared the case between in mechanical ventilation by air conditioners alone and in combined use of window opening after 160 seconds.
  • Ventilation speed increased several times by the combined use.
  • Henceforth, we plan to consider to extend to public transportation organizations such as taxi and bus.

Window closing during off-hours

Window opening During off-hours

Window closing when crowded

Window opening When crowded

Courtesy of RIKEN in cooperation with Toyohashi University of Technology and Kajima Corporation