Impact of subject position and cough direction on indoor coughing droplet dispersion and transmission using large eddy simulations

Abstract

Airborne transmission is an important route for infectious respiratory diseases, yet its dynamics beyond short-range distances remain underexplored. In this study, we investigated full-range transmission using large eddy simulations (LES), validated by particle image velocimetry (PIV) experiments, considering two subject positions and two cough directions. Within the short range (up to 2 m/20 s), airborne droplet concentrations decreased by one order of magnitude for every 0.5 m from the source, regardless of subject position or cough direction. In the medium (2–4 m/60 s) and long range (> 4 m), concentrations declined more gradually by two orders of magnitude, with subject position significantly influencing spatial distribution, but cough direction having little effect. Coughs originating from the center of the room resulted in much higher concentrations in the front half compared to the back, even after 600 s of mixing. In the short range, infection risk at the adult height of 1.6 m was substantially higher than at the child height of 1.2 m, whereas inclined coughs posed a greater risk to children than horizontal coughs. In the medium and long range, infection risks for adults and children were similar.