Mass Transfer: Corona Virus Spread due to a Cough in Open Air

Coronavirus Spread Due to a Cough in Open Air — ANSYS Fluent CFD Simulation Training

This project simulates the spread of coronavirus particles resulting from a human cough in open-air conditions, using ANSYS Fluent. When an infected person coughs, virus-laden particles disperse through the air and can potentially reach and infect a nearby healthy individual. Understanding this process, and determining the minimum safe distance needed to limit transmission, has become one of the most actively studied topics in CFD research, commonly referred to as social or physical distancing.

The model consists of a human figure placed within a cube-shaped domain representing the open-air environment, with the mouth defined as the source of virus-carrying droplets. The 3-D geometry was created using SolidWorks and Design Modeler, and meshed in ANSYS Meshing with an unstructured mesh, refined further near the mouth region. The total element count is 584,587.

Methodology

A two-way coupled Discrete Phase Model (DPM) is used to capture the unsteady behavior of the dispersed droplets and their interaction with the surrounding continuous airflow. The model accounts for stochastic collision, coalescence, and breakup of droplets. Droplets are injected at a temperature of 310 K, a velocity of 31.85 m/s, and a flow rate of 0.018 kg/s, released over a time interval of 0 to 0.1 s.

Since droplet sizes vary, the Rosin-Rammler logarithmic distribution is used to define the diameter range, including the minimum, maximum, and mean diameters, the spread parameter, and the number of diameter classes per injection. The Species Transport model is enabled alongside the droplet model to capture droplet evaporation, meaning the airflow field around the patient is solved together with species mixing.

Results

The simulation tracks the virus-laden particles over time, producing an animation that shows their release and gradual dispersal. Snapshots of the particle distribution at different time steps are also extracted. The results illustrate how the virus spreads during a cough event in open air, covering the period from 0.1 s to 1.75 s.