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Old   April 16, 2015, 11:25
Default Porous membrane modelling
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Cornelia Blanke
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I am trying to set up a model with several hundred of porous membranes of size 1.3mē each. Their thickness is 0.003m and their Darcy's coefficient is 10e+10 m^(-2) - quite high!

My first idea was to use a porousBafflePressure BC inside the simpleFoam solver. But I found out that this BC is really unstable: it is already quite hard to get converged a simple test case, and it seems to be impossible for my real model.

So I had a deeper look into porousSimpleFoam solver. With a test case I found out that I have to use a very fine mesh inside my porous media and also next to my porous media in order to predict the pressure loss through the membrane accurately. If I use only 1-2 cell layers inside my membranes, the pressure drop is computed much too low. For my real model I would get a crazy amount of cells...


So I wonder if somebody can share some experiences or ideas on how I can set up my model efficiently:
- How do you usually model your porous membranes? As porous baffle or as porous media?
- Is there a good way to converge the porousBafflePressure BC?
- How fine is your mesh?
- etc.
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Old   November 20, 2015, 06:17
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Hi,

I have a similar problem (simulation of pressure drop through a membrane). Did you find the answer to your questions? How did you proceed in your simulations?

Many thanks
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Old   November 20, 2015, 06:50
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Cornelia Blanke
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Hi Giack,

Unfortunately there is still no working solution inside the official version of OpenFoam. At the moment I still have to use a commercial solver for such cases.

But there is a small company in Germany that has developed an extended porousBafffle boundary condition. Their name is www.dhcae-tools.com. If you are interested and willing to spend some money, just have a look.

That is also my plan at the moment, to find out more about it.
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Old   October 13, 2016, 14:45
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Quote:
Originally Posted by Cornelia View Post
I am trying to set up a model with several hundred of porous membranes of size 1.3mē each. Their thickness is 0.003m and their Darcy's coefficient is 10e+10 m^(-2) - quite high!

My first idea was to use a porousBafflePressure BC inside the simpleFoam solver. But I found out that this BC is really unstable: it is already quite hard to get converged a simple test case, and it seems to be impossible for my real model.

So I had a deeper look into porousSimpleFoam solver. With a test case I found out that I have to use a very fine mesh inside my porous media and also next to my porous media in order to predict the pressure loss through the membrane accurately. If I use only 1-2 cell layers inside my membranes, the pressure drop is computed much too low. For my real model I would get a crazy amount of cells...


So I wonder if somebody can share some experiences or ideas on how I can set up my model efficiently:
- How do you usually model your porous membranes? As porous baffle or as porous media?
- Is there a good way to converge the porousBafflePressure BC?
- How fine is your mesh?
- etc.
Hi Cornelia,

could you tell me how did you set membrane properties in transportProperties file?
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Old   October 17, 2016, 09:19
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Hi to all,

I solved the problem using the fan boundary condition. You can create an internal patch (zero tichkness) with createBaffle and then use the fan boundary condition for the pressure field.

In this way you essentially create two coincident patches with cyclic behavior and impose a pressure drop through them.

I attached an example of the files p and createBaffleDict.

I hope it will be useful to you

createBafflesDict.txt

p.txt
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Old   January 30, 2017, 10:54
Default Nanofiltration modelling
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Jano van Rensburg
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Good day,

I am really new to CFD modelling.
I am trying to model an organic solvent nanoflitration system; ie a membrane system separating an organic compound and a homogeneous catalyst.
The catalyst must be rejected by the membrane.

I am not sure how to go about simulating a membrane?
I have read about porous mediums, but I am not sure if this will be suffice for my system?
Is there maybe a tutorial on membrane filtration I can study?

Any advice will be much appreciated.

Thank you
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Old   March 27, 2017, 08:19
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Hi to all,

I have to correct my previous statement. Indeed the fan BC is used for pressure rise, while for pressure drop the porousBafflePressure bc can be used.
I had the same problems described by Cornelia in the first post only for high values of the pressure drop. In these cases a stable solution can be reached decreasing the relaxation factors. I didn't experience any problem with this boundary condition till a pressure drop of the order of 700 Pa.
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Old   March 27, 2017, 08:20
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Hi to all,

I have to correct my previous statement. Indeed the fan BC is used for pressure rise, while for pressure drop the porousBafflePressure bc can be used.
I had the same problems described by Cornelia in the first post only for high values of the pressure drop. In these cases a stable solution can be reached decreasing the relaxation factors. I didn't experience any problem with this boundary condition till a pressure drop of the order of 700 Pa.
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