Dynamics of Turbulent Air Plumes Exhaled During Coughing: Insights from High-speed PIV Experiments

The transmission of infectious diseases relies on the movement of pathogen-laden droplets and aerosols expelled during human exhalations, which are part of a turbulent air plume. However, understanding the dynamics of this plume experimentally remains a challenge. To address this, we present an experimental framework utilizing Helium-Filled Soap Bubbles (HFSBs) to study the turbulent air plume exhaled during human coughing. We used HFSBs as tracers, which enabled the visualization of the plume using a high-speed camera and LED-based light sheet illumination. Through the application of image processing techniques, we isolate the turbulent air plume and analyse its trajectory. Our findings reveal a two-stage development of the plume. For the leading edge of the plume, we observed a travel distance of over 0.7 meters within 0.3 seconds, which implies a potential travel distance exceeding 2 meters within a second. To validate the accuracy of our results, we compared the outcomes of the image processing techniques with Particle Image Velocimetry (PIV). Moreover, our experiments facilitated the examination of the entrainment of ambient fluid into the plume. Future works will utilise the insights gained towards advancing infection control strategies through a comprehensive understanding of respiratory aerosol dynamics.