Experimental analysis of the air velocity and contaminant dispersion of human exhalation flows

What is it about?

Human exhalation flow is a potential source of pathogens that can constitute a cross-infection risk to people in indoor environments. Thus, it is important to investigate the characteristics of this flow, its development, area of influence, and the diffusion of the exhaled contaminants. This paper uses phase-averaged particle image velocimetry together with a tracer gas (CO2) to study two different exhalation flows over time: the exhalation of an average male (test M) and an average female (test F), using a life-sized thermal manikin in a supine position. The exhalation jets generated for both tests are similar in terms of symmetrical geometry, vorticity values, jet opening angles, and velocity and concentration decays. However, there is a difference in the penetration length of the two flows throughout the whole exhalation process. There is also a time difference in reaching maximum velocity between the two tests. It is also possible to see that the tracer gas dispersion depends on the momentum of the jet so the test with the highest velocity decay shows the lowest concentration decay. All these results are of interest to better understand cross-infection risk.

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Why is it important?

The experimental results of this study add further knowledge about the transient characteristics of male and female exhalation flows, quantifying their differences. These results are valuable for studying a long-distance dispersion of exhaled contaminants and therefore a possible cross-infection risk situation. The data may be used as boundary conditions or validation data for computational fluid dynamics simulations.