Sneezing is an explosive event. There are some who can sneeze unobtrusively into their handkerchief but more often than not it is an involuntary, uncontrollable reaction of the body to tinkling in the nostrils. Why would anybody want to analyse sneezing?
Lydia Bourouiba's area of research is the interface of Fluid Dynamics and Epidemiology. A faculty at the MIT, Cambridge, USA, she with her research team is in the process of understanding the fluid dynamics of sneezing. It is a well accepted fact that fluids expelled by an infected person during a sneeze or a cough have the potential to infect those who are nearby. If this violent expiratory event, as Bourouiba describes sneezing, could be well understood in terms of how far the pathogens could be propelled, then public health officials could put in place appropriate programs for the containment of contagious diseases.
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| A sneeze in progress: courtesy wikipedia For videos taken by Bourouiba's group visit Video Gallery |
A " let go " sneeze has been vividly captured in the picture shown. Aerogel particles spewed out by the sneezer (if I may use the term) spread and eventually disappear into the air. Bourouiba and her team are concerned about how fast and how far the aerosol particles can travel. Healthy volunteers were invited to participate in a study and their nostrils were tingled in the old fashioned way to induce sneeze. The research team then captured the entire event using ultra high speed cameras.
Violent expulsion of air -saliva mixture formed an elongated cone of turbulent cloud which expanded and spread around. (The dynamics has marked differences from the focussed high pressure spray from an aerosol can). The team was surprised to find that aerosol droplets could reach as high as the ceiling and as far as the end of he room. They also observed that the droplets could persist in the air for almost 10 minutes. In a follow up study the team took 8000 frames per second to film the entire process of sneezing. Replaying it later in slow motion, they saw that fluid mixture is expelled as a sheet which breaks up into rings as air pokes holes in the sheet, the rings then elongated into filaments and ultimately formed droplets. Droplets are then transported through the air by diffusion. The diffusion controlled movement of aerosol droplets in confined spaces such as inside a cinema hall or an aeroplane is what interests Bourouiba and her team. They want to understand how the logistics of airflow within the confined space, ambient temperature, humidity, etc. will influence aerosol size and transport.
References
1. Where sneezes go- Corie Lok, Nature pages 24-26 vol. 534, 2 June 2016.
2. Bourouiba Group
Violent expulsion of air -saliva mixture formed an elongated cone of turbulent cloud which expanded and spread around. (The dynamics has marked differences from the focussed high pressure spray from an aerosol can). The team was surprised to find that aerosol droplets could reach as high as the ceiling and as far as the end of he room. They also observed that the droplets could persist in the air for almost 10 minutes. In a follow up study the team took 8000 frames per second to film the entire process of sneezing. Replaying it later in slow motion, they saw that fluid mixture is expelled as a sheet which breaks up into rings as air pokes holes in the sheet, the rings then elongated into filaments and ultimately formed droplets. Droplets are then transported through the air by diffusion. The diffusion controlled movement of aerosol droplets in confined spaces such as inside a cinema hall or an aeroplane is what interests Bourouiba and her team. They want to understand how the logistics of airflow within the confined space, ambient temperature, humidity, etc. will influence aerosol size and transport.
References
1. Where sneezes go- Corie Lok, Nature pages 24-26 vol. 534, 2 June 2016.
2. Bourouiba Group
