Learning Forum

[yusra abuzar]

Hi,

I'm trying to do a multiphase VOF model with phase 1 as air and phase 2 as CO2 in a hospital room. I want to show how infected particles flow from a patient's mouth. I have 3 inlets, 3 outlets, 3 lighting fixtures and 3 manikins out of which one of them is the infected patient. The mouth of the patient is considered as a velocity inlet with a magnitude of 0.9 m/s and direction in +Y direction (need to show it flowing outwards from the mouth). The inlet has a velocity of 3 m/s. The volume fraction of the mouth is taken as 1 and for the inlet as 0.

However, after initilializing the contours of volume fraction gives a min and max range of 0 and nothing is seen. The velocity seems to be working though. I checked the vector contour to see if the flow of co2 from the mouth is in the right direction and it is flowing outwards, but the volume fraction does not seem to be computed. Please let me know how I can resolve this issue urgently!!

[Omkar Pawar]

Hi, 

VOF Multiphase model is a free surface modelling technique, that helps to locate and track free surface.

This is suitable for simulation which involve distinct demarcation between two phases.

An example, suitable for VOF simulation would be a system with air and water interaction (flow of river in air domain, bottle filling simulation etc), flow of two immiscible liquids (oil and water in vessel etc).

The phase interaction in the above example is such that the fluid is continuous in regards to both phases.

Now regarding your problem, the following interaction are involved in your simulation domain,
1. Air and CO2 (this are miscible fluids)
2. Infected droplets (This would be as a dispersed phase. i.e. infected droplets present at discrete location in the continuous domain of air and CO2.

The appropriate modelling approach in this case would be to do a single-phase simulation (with species transport turned on to capture interaction of CO2 and air) with Discrete Phase Modelling (DPM to model the transport of infected particles).