The influence of human walking on dispersion of respiratory droplets in a ceiling-based mixing ventilation chamber

Recent research works indicate that in an indoor space human walking can causestrong secondary airflow and thus influence the distribution of airborne infectiousparticles. Respiratory droplets exhaled by infectious patients can disperse differentlyunder different ventilation schemes. In Hong Kong the conventional ceiling-basedmixing ventilation scheme is popularly in use. The extent of human walking undersuch a ventilation scheme that affects the dispersion of respiratory droplets was sofar rarely reported. In this study, a numerical investigation on the impact ofdifferent human walking speeds on the dispersion of respiratory droplets in aceiling-based mixing ventilation chamber was performed. A numerical model,previously developed by our group, was adopted by applying the Lagrangianmethod for tracing the motion of droplets, the dynamic mesh model for describinghuman walking, and the Eulerian RANS model for solving the airflow. The validityof this numerical model has been checked against literature data. The results showthat under the influence of human walking, respiratory droplets can be entrained bythe wake of the walking man. Accordingly, the trajectories and fates of droplets canbe changed by the walking manner. Faster walking speeds are able to mix thedroplets more uniformly and quicker. To reduce the short-term exposure risk, theappropriate distance between the source man and the susceptible walking manneeds to be further explored in future study.