Covid-19: Consideration for Wearing Shields, ANSYS Fluent Simulation Training

Description

This project has tried to simulate the release of coronavirus particles from a patient’s mouth while talking and using a shield to prevent transmission to another person using ANSYS Fluent software.

One of the most important recommendations of doctors regarding preventing disease transmission between people is the use of special masks or shields at low social distances. The present model is designed in three dimensions using Design Modeler software.

The model’s geometry includes a computational space measuring 1.6 m * 2 m * 2.6 m in which two people are facing each other at a distance of 80 cm. One of these two people is designed as a patient, so the patient’s mouth is defined as the source of the virus spread caused by talking.

The meshing of the model has been done using ANSYS Meshing software. The element number is 724076.

Also, a transient solver has been used due to the nature of the project (i.e., particle/virus dispersion).

Methodology

This study aims to investigate the ability of virus particles to propagate and transmit at a distance less than a social distance. For the present simulation, the discrete phase model (DPM) is used; Because this model allows us to study a mass of particles discretely or bit by bit in a continuously fluid space.

Due to this model’s choice, the virus particles secreted from the patient’s mouth are considered a discrete phase. The open airflow in the computational area is regarded as a continuous phase.

The type of discrete phase behavior will be time-dependent and with an aSurfacetep of 0.001 s (by Activ surface unsteady particle tracking mode).

After activating the discrete phase model, the Injection process must be defined, determining the type and quality of discrete particles injected into the model.

After activating the discrete phase model, the injection process must be defined, determining the type and quality of discrete particles injected into the model. In this model, the emitted particles are defined as Inert type, and the injection type is surface and is done through the surface of the patient’s mouth.

These virus particles have a constant diameter of 0.000001 m and a temperature of 310 K, which are spread between 0 s and 20 s.

A specific Profile has been used to define the velocity and flow rate of coronavirus particles exiting the mouth. This profile shows the velocity and diffusion of emitted particles when speaking.

This way, these virus particles are removed from the patient’s mouth time-dependent. The particle velocity profile is defined as a sinusoidal function with a maximum velocity of 0.33 m/s, and the particle flow rate is defined by a specific ratio to the particle velocity.

Also, the boundary conditions related to the discrete phase model are defined so that the particles in the boundary related to the patient’s mouth have an Escape state, meaning that the particles pass through this boundary.

Masks or shields mounted on the patient’s face have a Trap mode, meaning particles are trapped and accumulate within these boundaries.

Also the RNG k-epsilon model and energy equation also surfaced to solve the turbulent fluid equations and calculate the temperature distribution inside the domain, respectively.

Conclusion

At the end of the solution process, the particle tracking of the virus particles at different time intervals of the simulation process is obtained. This particle sequence is based on the Residence Time and the velocity of the particles.

As seen from the images and according to the simulation process defined, the virus particles are expelled periodically from the patient’s mouth in 20 s.

According to the pictures, it can be concluded that the presence of a shield causes the virus particles to come out of the patient’s mouth to accumulate on the shield and not be transmitted to a healthy person.