The University of Twente’s TechMed Centre has developed a unique test setup that shows airflows in real time. The images provide a good indication of how aerosols spread and are being used to gain fresh ideas for solutions that could help to fight the coronavirus. The setup enables the effect of face masks to be measured and ventilation solutions for public transport and theatres to be tested.
‘Businesses in various sectors are very interested in using our test setup’, says Prof. Ruud Verdaasdonk, who recently built the airflow test setup. ‘Known as an RT-BOS (Real-Time Background Oriented Schlieren) setup, it provides a very good understanding of air movements when people talk, cough and sing, for example’. Detlef Lohse, UT chair of Physics of Fluids, had previously done various experiments to gain an understanding of air movements during these actions, and what a safe distance should therefore be.
Verdaasdonk draws some preliminary conclusions from measurements and puts forward suggested solutions. ‘The tests showed that almost all the face masks currently in use leak at the edges, but they do capture small droplets and vapour effectively. Also, it would seem to be safer to cough downwards into your shirt or blouse than into your elbow. The safest way is to pull the front of your collar out first. If you cough or sneeze into your elbow, that in fact narrows the opening, making the airflow escape along your arm more rapidly. If you cough into your shirt, the air and droplets do not spread any further. This has been confirmed using a test setup designed specifically to visualise droplets as used by Lohse.’
Further research is needed to establish how droplets spread during various movements and under various conditions such as high and low humidity, so as to gain a clear idea of a safe distance during the various activities.
The RT-BOS test setup enables the ventilation of a space to be observed on a large scale. There is great interest in this at present. Various businesses have asked the researchers to look into ventilation solutions for large spaces in relation to COVID-19, namely air circulation in train compartments and theatres.
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Ruud Verdaasdonk is Professor of Health Technology Implementation at the University of Twente’s TechMed Centre. Prof. Detlef Lohse is Chair of Physics of Fluids at the University’s Mesa+ Centre. They are just two of the many professors who are taking up the fight against the coronavirus.