[Rui_27]

Hello to all,

I would like to know how to set the volume fraction of one phase in a VOF calculation equal to 0 during the entire simulation. It could be through the GUI or by a UDF.

Basically I want to prevent phase-2 to enter into a cell zone, but allow the passage of phase-1.

Any ideas?

Thanks in advance.

Best regards.
Rui

[Dave_88]

Why would you need a multiphase model, if you do not want the second phase to flow during the entire calculation?

[Rui_27]

I don't want the second phase to flow in just one of the cell zones that composes my domain. In the rest of the domain yes, I want the second phase to flow.

I already tried something with DEFINE_ADJUST and seems promising. I will post the the solution, in case it works.

Rui

[hwet]

how is that physical though? why cant the other phase go there, any special reasons?

Making it become 0 through a UDF is not the right way i think, since it will be like a sink source then. your phase will go there but be taken out of the simulation which will in turn affect the phase volume fraction in other regions of the geometry.

[Rui_27]

My domain consists in two zones. One is a channel in a form of a serpentine and the other is a porous media. Air (phase-1) enters into the channel and flows to the bottom of the porous media, where it is consumed and water is produced. Some of the water produced condensates and accumulates in the system. Attached is a image of it.

For the porous media, I am using a UDS (within phase-1) to account for the transport of water within it. Then, based on the water present in the interface between the porous media and the serpentine channel, I obtain the water (phase-2) velocity in each of the pores that are drawn in the channel bottom surface.

Since I already account for water transport in the porous media through a UDS, I do not want water from phase-2 in the porous media as well. Ideally I would like the interface between the two zones to be a wall for phase-2, but not to phase-1, because I need air to enter into the porous media for the reaction of water formation to occur. Is it possible to do that?

In fact that's what occurs in real systems (PEM fuel cells). Water produced flows through the porous media and emerges in the channel as droplets, them these droplets grow to have a much larger diameter than the pores of the porous media, and therefore it works like a wall for water, which is reinforced by the fact the the porous media is typically hydrophobic.

So any ideas on how to prevent water from entering into the porous media?

I also thought about increasing (a lot) the permeability of water (phase-2) in the porous media, that would also prevent water entrance, what do you think?