Description

This project uses ANSYS Fluent to simulate how coronavirus-laden droplets released during speech can travel at sub–social-distance separations. We conduct and analyze the CFD study to assess transmission risk while talking.

The scenario models exhaled particles from an infected speaker and their transport toward another person within a defined indoor volume. Geometry is built in DesignModeler as a 3D domain measuring 1.6 m × 2 m × 2.6 m, with two individuals facing each other 0.8 m apart. The infected person’s mouth serves as the particle source.

Meshing is performed in ANSYS Meshing, producing 724,076 elements. Because dispersion evolves over time, a transient solver is employed.

Talking Methodology

To capture particle transport and deposition, the discrete phase model (DPM) is used, treating droplets as a dispersed phase moving through a continuous air field. Unsteady particle tracking is enabled with a 0.001 s time step.

An injection is defined at the mouth surface with inert particles of 1×10⁻⁶ m diameter and 310 K temperature, released from 0 to 20 s. A custom profile prescribes the particle velocity and mass flow rate during speech, with a sinusoidal velocity history peaking at 0.33 m/s and the mass flow rate tied proportionally to that velocity. Turbulence is modeled with RNG k–ε, and the energy equation is solved to capture temperature effects.

Talking Conclusion

Post-processing provides particle tracks at multiple times, reported by residence time and instantaneous velocity. The results show particle emission occurs during the first 20 s; during the subsequent 20 s, only previously emitted particles continue to move within the gap between the individuals. Overall, the simulation indicates that speaking for 20 s without a mask can lead to particles reaching the other person by about 40 s, potentially exposing them to the virus.