Influence of viseme-inspired orifice shapes on the dispersion of expiratory events

It is well established that diseases can be spread via airborne transmission, sourced from expiratory events such as speech, coughing and sneezing. As these events are pulsatile in nature, it is important to study the influence of pulsatility on the flow dynamics of these events. In this work, the influence of mouth shape (inspired by visemes, i.e. sounds that look the same) on the dispersion of pulsatile expiratory aerosols is studied to help understand and mitigate the spread of airborne diseases. A custom-built pulsatile coughing simulator is used to generate single- and multi- pulsed coughs of varying cough peak flow rates (CPFR). Five static, interchangeable elliptical orifice shape fittings (e = 0, 0.70, 0.85, 0.95, 0.99) representing different visemes are 3D printed and attached to the outlet of the simulator. Each fitting has a cross-sectional area equivalent to a circle with diameter D=1in. The penetration distance of both single- and double-pulsed coughs are measured using smoke flow visualization for each case. Particle image velocimetry is used to measure the exit velocity profile and maximum axial velocity over time at the mouth outlet. It is observed that the axial exit velocity and penetration distance are both higher for orifice shapes with larger eccentricities.