Cough Virus Particles Dispersion in a Coffee Shop

Description

This project simulates the dispersion of human cough virus particles inside a coffee shop using ANSYS Fluent, investigated through CFD analysis. Studying how respiratory droplets travel through an indoor space is a core biomedical and public-health concern, since it informs how airborne infections spread in crowded environments and how such spaces might be made safer.

The model was built in 3D using Design Modeler, with the computational domain representing the interior of a coffee shop. Meshing was performed in ANSYS Meshing using an unstructured grid, with the curvature method applied to refine the mesh in grid-sensitive regions; the total cell count is 4,578,388. Because of the time-dependent nature of the problem, a transient solver was used.

Methodology

Here, ANSYS Fluent simulates the human cough virus particles using a two-way coupled Discrete Phase Model (DPM), in which the particles and the surrounding air influence one another. Following this injection definition, the virus particles are physically expelled from the patient's mouth as water droplets that evaporate in the surrounding air.

These droplets have a temperature of 310 K, a velocity of 31.85 m/s, and a mass flow rate of 0.018 kg/s, released over the interval from 0 s to 0.1 s. The droplet diameter is not constant during propagation; instead, the Rosin-Rammler logarithmic distribution is used to characterize the range of droplet sizes. Through this method and its associated formulation, the minimum, maximum, and average diameters, the spread (exponential) parameter, and the number of diameter classes per injection are all defined. The droplet (drop) mode is applied together with the activated Species Transport model, allowing the evaporation of the droplets to be captured.

The discrete-phase boundary conditions are defined as follows: the patient's mouth is set to Escape, meaning particles pass through this boundary; the surfaces of people's bodies and all the table and chair walls use the wall-film mode; and the floor uses the Trap mode, so that particles reaching it are captured and accumulate there. The simulation is unsteady, run over a 3 s interval with a time step of 0.01 s. The RNG k-epsilon model, together with the energy equation, was enabled to resolve the turbulent flow and compute the temperature distribution throughout the domain.

Analysis

On completion of the solution, the virus particle tracking at the final second of the simulation was obtained, based on the residence time of the particles. An animation of the virus dispersion and its gradual disappearance over time was also exported, showing how the droplets spread through the coffee shop and where they ultimately settle — offering insight into airborne transmission risk and the distribution of contamination across surfaces within an indoor public space.