Outlet for only one phase?

Monsieur · December 13, 2018, 02:49

Can anyone help me...even Ansys Support can´t give me a satisfactorily answer
I have an two-phase (oil and air) flow in a porous medium. The porous media is a filter where the flow is from inside to outside. The outside is an outlet for both phases (pressure outlet). Now I want that the bottom of the filter is an outlet only for the oil phase. Is there a way to handle this, like a permeable wall or pressure outlet only for oil?
A velocity outlet with or mass flow outlet with only oil isn´t a possibility because so I have to set the outflow of the drainage and the outflow should adjust dependent on the oil saturation in the filter.

It would be stunning if anyone has an idea to solve this task.

Per_Holmgren · October 3, 2019, 12:20

Can't give an answer, but I have a similar problem. I essentially want to define a mass outlet that is only permeable for the heavy phase (so the opposite of a degassing boundary).

Making a UDF that allows you to specify what phase can pass though a boundary would be really nice (instead of only having the default degassing boundary), but I haven't found a way to do that.

BlnPhoenix · October 8, 2019, 04:46

Quote:

Originally Posted by Per_Holmgren

Can't give an answer, but I have a similar problem. I essentially want to define a mass outlet that is only permeable for the heavy phase (so the opposite of a degassing boundary).

Making a UDF that allows you to specify what phase can pass though a boundary would be really nice (instead of only having the default degassing boundary), but I haven't found a way to do that.

What kind of solver are you using? VOF, E-E..?

Per_Holmgren · October 8, 2019, 05:43

E-E. I figured out that you can use a velocity inlet boundary with a negative velocity udf for the solid phase, and the gui inputs for the gas phase, and you get the solid going out and the gas going in without the pressure going crazy.

It works for me, but is not perfect.

I guess one could tweak the code found here
http://www.afs.enea.it/project/neptu...udf/node49.htm
And just switch the super_tread and sub_tread commands to point at the secondary phase.

But I haven't done that yet, I'm stuck at other stuff.

BlnPhoenix · October 8, 2019, 05:49

Yes, that's what i would have suggested for the UDF.
I think you would need also the alpha values in the cell next to the boundary face and patch that as the BC for alpha, since a zeroGradient BC is not implemented in Fluent as far as i know.. Then set a velocity for the permeable phase and set the velocity to zero for the non permeable phase.. It's doable with UDF programming..

December 13, 2018, 02:49	Outlet for only one phase?	#1
Monsieur New Member Join Date: Nov 2018 Posts: 3 Rep Power: 8	Can anyone help me...even Ansys Support can´t give me a satisfactorily answer I have an two-phase (oil and air) flow in a porous medium. The porous media is a filter where the flow is from inside to outside. The outside is an outlet for both phases (pressure outlet). Now I want that the bottom of the filter is an outlet only for the oil phase. Is there a way to handle this, like a permeable wall or pressure outlet only for oil? A velocity outlet with or mass flow outlet with only oil isn´t a possibility because so I have to set the outflow of the drainage and the outflow should adjust dependent on the oil saturation in the filter. It would be stunning if anyone has an idea to solve this task.

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October 3, 2019, 12:20		#2
Per_Holmgren New Member Västerbotten Join Date: Sep 2016 Posts: 23 Rep Power: 10	Can't give an answer, but I have a similar problem. I essentially want to define a mass outlet that is only permeable for the heavy phase (so the opposite of a degassing boundary). Making a UDF that allows you to specify what phase can pass though a boundary would be really nice (instead of only having the default degassing boundary), but I haven't found a way to do that.

October 8, 2019, 05:43		#4
Per_Holmgren New Member Västerbotten Join Date: Sep 2016 Posts: 23 Rep Power: 10	E-E. I figured out that you can use a velocity inlet boundary with a negative velocity udf for the solid phase, and the gui inputs for the gas phase, and you get the solid going out and the gas going in without the pressure going crazy. It works for me, but is not perfect. I guess one could tweak the code found here http://www.afs.enea.it/project/neptu...udf/node49.htm And just switch the super_tread and sub_tread commands to point at the secondary phase. But I haven't done that yet, I'm stuck at other stuff.

October 8, 2019, 05:49		#5
BlnPhoenix Senior Member Join Date: Aug 2014 Location: Germany Posts: 292 Rep Power: 14	Yes, that's what i would have suggested for the UDF. I think you would need also the alpha values in the cell next to the boundary face and patch that as the BC for alpha, since a zeroGradient BC is not implemented in Fluent as far as i know.. Then set a velocity for the permeable phase and set the velocity to zero for the non permeable phase.. It's doable with UDF programming..