Séance Séminaire

Séminaire des Doctorant·e·s

Numerical simulations of human expiratory flows

Air flows generated during human expiratory activities, such as speech, breathing, laughing, etc., can be a viable pathway for the transmission of air- borne viruses. The prevalence of asymptomatic transmission of the SARS-CoV- 2 virus have raised a growing need both among the research community and public health institutions to understand air flows and aerosol transport occur- ring during social interactions. We aim to these efforts and perform large-eddy simulations of expiratory flows generated during laughing, nasal breathing and their interaction with a horizontal table placed below the mouth of the speaker, obstructing the vertical penetration of the air flows. We document the effect of this interaction on turbulent transport and short-range transmission risk of potentially infectious, expiratory droplets. This analysis is complemented with a simulation that addresses a relatively realistic social interaction in which two individuals sitting opposite to each other, one of whom is speaking, other is breathing around a table. The study reveals salient features of the expiratory flows with regard to the effect of the table. Under the conditions explored, minimal interactions of the flows exhaled during speech and table is observed. However, the distance fixed by the table is sufficient to have short-range airborne transport to the other person, both due to the forward flow associated with plosive sounds and the downward flows generated by fricatives. On the opposite, nose-breathing and laughing flows strongly interact with the table. Their impact causes the jet to deviate earlier than free-jets, with two consequences: aerosols reach the individual sitting opposite to the emitter earlier and with a higher concentration, increasing transmission risk.