Flow with counterflow and porous membrane (Ansys CFX)

abcde89837893 · February 17, 2025, 05:32

Hi,
I need help with a project with Ansys CFX where I have a pipe flow in positive x_direction, a porous domain around it and another pipe with a flow in negative x_direction around the porous domain. I want to calculate with water everywhere. For the porous domain, I have information on porosity and permeability. I would like to specify the velocity at the inlet of the inner and outer flow and the ambient pressure at the outlet of the two flows. I have chosen k-Epsilon as the turbulence model. I have already found the 'constant domain physics' setting. It also flows in countercurrent. Now to the problem. Nothing flows through the porous domain and I don't know why. The pressure and velocity are always zero. Maybe someone has an idea and can help me. Thanks for reading.

Gert-Jan · February 18, 2025, 03:09

probably you have 3 volumes that have nothing in common.
Are they connected properly using an interface?
Better share a screendump of CFX- Pre so we can get a better picture.

abcde89837893 · February 21, 2025, 12:35

Hey,
thanks for the answer. I am pretty sure that I have set the interfaces correctly. If I set up exactly the same with a rectangular pipe cross section, i.e. a flow in the positive x-direction at the bottom, the porous membrane above and a flow in the negative x-direction at the very top with a flow through the porous domain exclusively in the y-direction, I get a result. I have also tried it with a quarter of the tube, there too I have a flow through the porous membrane. Only when I simulate it with the whole tube do I get no flow through the membrane. I don't understand this at all and can't explain it to myself. I have set exactly the same for all three variants.

Gert-Jan · February 27, 2025, 02:27

probably the setup is not exactly the same.
If you don't share more details (screenshots, outputfiles, etc), we cannot help you.

February 17, 2025, 05:32	Flow with counterflow and porous membrane (Ansys CFX)	#1
abcde89837893 New Member Join Date: Feb 2025 Posts: 2 Rep Power: 0	Hi, I need help with a project with Ansys CFX where I have a pipe flow in positive x_direction, a porous domain around it and another pipe with a flow in negative x_direction around the porous domain. I want to calculate with water everywhere. For the porous domain, I have information on porosity and permeability. I would like to specify the velocity at the inlet of the inner and outer flow and the ambient pressure at the outlet of the two flows. I have chosen k-Epsilon as the turbulence model. I have already found the 'constant domain physics' setting. It also flows in countercurrent. Now to the problem. Nothing flows through the porous domain and I don't know why. The pressure and velocity are always zero. Maybe someone has an idea and can help me. Thanks for reading.

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February 18, 2025, 03:09		#2
Gert-Jan Senior Member Gert-Jan Join Date: Oct 2012 Location: Europe Posts: 1,964 Rep Power: 28	probably you have 3 volumes that have nothing in common. Are they connected properly using an interface? Better share a screendump of CFX- Pre so we can get a better picture.

February 21, 2025, 12:35		#3
abcde89837893 New Member Join Date: Feb 2025 Posts: 2 Rep Power: 0	Hey, thanks for the answer. I am pretty sure that I have set the interfaces correctly. If I set up exactly the same with a rectangular pipe cross section, i.e. a flow in the positive x-direction at the bottom, the porous membrane above and a flow in the negative x-direction at the very top with a flow through the porous domain exclusively in the y-direction, I get a result. I have also tried it with a quarter of the tube, there too I have a flow through the porous membrane. Only when I simulate it with the whole tube do I get no flow through the membrane. I don't understand this at all and can't explain it to myself. I have set exactly the same for all three variants.

February 27, 2025, 02:27		#4
Gert-Jan Senior Member Gert-Jan Join Date: Oct 2012 Location: Europe Posts: 1,964 Rep Power: 28	probably the setup is not exactly the same. If you don't share more details (screenshots, outputfiles, etc), we cannot help you.