SKM 2021 – scientific programme

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SYCO: Symposium The Physics of CoViD Infections

SYCO 1: The Physics of CoViD Infections

SYCO 1.4: Invited Talk

Monday, September 27, 2021, 15:15–15:45, Audimax 1

Extended lifetime of respiratory droplets in a turbulent vapor puff and its implications on airborne disease transmission — •Detlef Lohse, Kai Leong Chong, Chong Shen Ng, Naoki Hori, Morgan Li, Rui Yang, and Roberto Verzicco — Physics of Fluids Group, University of Twente, Enschede, The Netherlands

Long-range airborne transmissions of viruses encapsulated in droplets play a major role in the transmission of respiratory diseases. I will show direct numerical simulations of a typical respiratory aerosol within a Lagrangian-Eulerian approach, coupled to the ambient velocity, temperature, and humidity fields to allow for exchange of mass and heat and to realistically account for the droplet evaporation. We found that for an ambient relative humidity of 50% the lifetime of the smallest droplets of our study with initial diameter of 10 μm gets extended by a factor of more than 30 as compared to what is suggested by the classical picture of Wells, mainly due to the role of the respiratory humidity, while the larger droplets basically behave ballistically. With increasing ambient relative humidity the extension of the lifetimes of the small droplets further increases and goes up to 150 times for 90% relative humidity, implying more than two meters advection range of the respiratory droplets within one second. For low ambient temperatures the problem is even more serious, as the humidity saturation level of air goes down with decreasing temperature. We anticipate our approach to be a starting point for larger parameter studies and for optimizing ventilation and indoor humidity controlling concepts, which both will be key in mitigating the COVID-19 pandemic.