Cough in a Car: Corona Virus spread

Corona Virus Spread in a Car Due to the Cough of the Driver, CFD Simulation Tutorial by ANSYS Fluent

Description

This project simulates coronavirus spread within a car's interior resulting from the driver's cough, using ANSYS Fluent. COVID-19 has posed one of the greatest global health challenges, largely due to its high contagion rate — coughing or sneezing without a mask can readily spread the virus within enclosed spaces. Maintaining social distance in closed environments has consistently been recommended as a key preventive measure, and the interior of a passenger car represents exactly this kind of confined space where virus transmission between occupants becomes a concern.

This simulation models the release of virus particles from the mouth of an infected driver within a car's interior, aiming to investigate how strongly these particles diffuse throughout the enclosed cabin space.

The geometry was designed in Design Modeler, representing a car interior with a driver modeled seated in the driver's seat. The domain was meshed in ANSYS Meshing using an unstructured grid totaling 290,403 cells.

Methodology

The Discrete Phase Model (DPM) was used to track the virus-laden particles individually within the continuous airflow inside the car. The wet virus particles secreted from the driver's mouth were treated as the discrete phase, with the surrounding cabin airflow as the continuous phase. Several physical sub-models were applied to these discrete particles: 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). The discrete phase behavior was tracked using unsteady particle tracking with a time step of 0.001 s.

Injected particles were defined as water droplets, with water vapor modeled as an evaporating gas species — this droplet-based approach required activating the Species Transport model alongside DPM, tracking three gas species throughout the domain: oxygen (O₂), nitrogen (N₂), and water vapor (H₂O), with air serving as the primary fluid throughout the cabin.

Conclusion

Results include particle tracking of the virus particles at multiple time intervals, based on each particle's residence time and diameter. This tracking clearly illustrates the spreading pathway of the virus particles throughout the car's interior, revealing the strength and extent of the spread. After a brief period, these particles begin to disperse further or settle onto the car's interior surfaces — offering insight into both the transmission risk posed by an infected driver and the practical timeframe over which airborne virus concentration within the vehicle diminishes.