COVID-19 Transmission While Talking

Description: This project uses ANSYS Fluent to examine how virus-laden droplets expelled during speech can travel across sub-social-distance separations, assessing transmission risk when two people converse in close proximity without masks.

Methodology: The scenario models an infected speaker's exhaled particles traveling toward a second person within a 3D indoor volume measuring 1.6 m × 2 m × 2.6 m, built in DesignModeler with the two individuals positioned 0.8 m apart facing each other and the infected person's mouth acting as the particle source. The domain is meshed in ANSYS Meshing with 724,076 elements, and since droplet dispersion evolves over time, a transient solver with a 0.001 s time step is used. The Discrete Phase Model tracks inert particles of 1×10⁻⁶ m diameter released at 310 K from the mouth surface between 0 and 20 seconds, driven by a custom sinusoidal velocity profile peaking at 0.33 m/s with mass flow rate scaled proportionally; turbulence is captured with the RNG k–ε model, and the energy equation is solved to account for temperature effects.

Analysis: Particle tracks are reviewed at multiple time steps, reported by residence time and instantaneous velocity, showing that particles are actively emitted during the first 20 seconds while the following 20 seconds involve only the continued drift of previously released particles across the gap. The results indicate that just 20 seconds of unmasked conversation can allow droplets to reach the other person by roughly 40 seconds, highlighting a realistic exposure risk during ordinary close-range talking.