An experimental framework to capture the flow dynamics of droplets expelled by a sneeze

Respiratory activities such as sneezing generate pathogen laden droplets that can deposit in the respiratory tract of a susceptible host to initiate infection. The extent of spread of these droplets determines the safe distance between a patient and health care worker. Here, we have presented a method to visualize the droplets expelled by a sneeze using light-sheet illumination. This method of visualization provides images that clearly resolve the velocities of droplets with minimal overlapping trajectories, towards understanding their flow dynamics. Furthermore, we present the image processing techniques required to perform accurate Particle Tracking Velocimetry to understand the motion of expelled droplets. Flow fields are presented from applying this methodology over multiple sneezes which reveal that less than 1% of droplets expelled travel at velocities greater than 10 m/s and almost 80% of droplets travel at velocities less than 5 m/s. Furthermore, we observe that some droplets are generated by ligament breakup outside the mouth and some are generated within the respiratory tract.