Sneeze: Coronavirus Dispersion in an Elevator

Description

Coronavirus (COVID-19) has been widely recognized as one of the most significant global health challenges, both due to its danger to human health and its high transmissibility between infected and healthy individuals.

Coughing or sneezing without a mask is a primary mechanism for viral spread, which is why maintaining social distance has consistently been recommended by physicians as a key preventive measure. The elevator cabin represents a particularly high-risk environment in this context, since multiple people are often confined to a small space at minimal distance from one another, typically with limited ventilation.

This project uses CFD methods in ANSYS Fluent to simulate the dispersion of coronavirus particles released by a coughing patient inside an elevator cabin. The computational domain models two individuals within the cabin: one representing an infected patient who coughs or sneezes, and the other positioned at a defined distance, representing a person potentially exposed to the released virus particles. The goal is to evaluate how effectively virus particles disperse within the confined elevator space and assess the likelihood of transmission to the second occupant.

The cough is modeled as an injection of virus-laden water droplets expelled from the patient's mouth as they evaporate into the surrounding air. These droplets are released at a temperature of 310 K, a velocity of 31.85 m/s, and a mass flow rate of 0.018 kg/s, over an interval of 0 to 0.1 seconds. Since droplet diameter varies during propagation, a Rosin-Rammler logarithmic distribution is used to represent the range of particle sizes.

The 3D geometry was built using SolidWorks and Design Modeler, and meshed in ANSYS Meshing with an unstructured mesh of 454,433 elements.

CFD Methodology

This simulation uses the Discrete Phase Model (DPM), which enables the study of a discrete particle mass suspended within a continuous fluid domain. Here, the virus-laden droplets released from the patient's mouth are treated as the discrete phase, while the airflow moving through the elevator's ventilation system represents the continuous phase.

Several physical sub-models are applied to the discrete particles, including two-way turbulence coupling (capturing the mutual interaction between the continuous and discrete phases), stochastic collision (irregular droplet-to-droplet collisions), coalescence (droplet merging), and breakup (droplet disintegration). Based on this framework, parameters such as minimum, maximum, and mean droplet diameter determine the spread exponent and the number of diameter classes considered per injection.

The droplet-based approach is applied alongside an activated species transport model, while the energy equation is enabled to account for temperature variation throughout the domain.

Conclusion

At the end of the simulation, virus particle tracking is obtained at the final time step, based on residence time and particle diameter. An animation depicting virus dispersion and its gradual disappearance over time is also generated and included in the project deliverables.

Additionally, three-dimensional contours are produced showing temperature distribution, the mass fraction of oxygen introduced by the ventilation system, and the spread of water droplets released during the cough — together illustrating how ventilation airflow influences the containment or dispersion of airborne viral particles within the elevator cabin.