Mass diffusion (ie air or oxygen) through membrane

zania · March 28, 2013, 06:11

Hi
I am new to OpenFoam and I just managed to run the planeWall2D tutorial (I am not quit sure about all the files).
To study:
Fluid mass diffusion (ie air or oxygen) through membrane (ie food bag). Next I will have platelets in it (rectangular leaving polymer space about its dimensions around it).
Fick's first law is applicable, the diffusive mass flux

or the analogue Fourier’s Law of Heat Conduction Heat flux (W/m2)

Q1) Is there a solver for mass flux?
Q2) What is the appropriate solver (laplasianfoam is only for the second law?)
Q3) To start could I use files from the planeWall2D tutorial (leaving out the boundaries near the wall ?
Q3.1)Is there a simpler tutorial similar to my case?
Q4) In the planeWall2D tutorial if I manage to change the 1)dimensions for mass-diffusivity and concentration 2)The value of high and low concentration 3) the mass-diffusivity, would that be enough for a start?
Q5) Would be easier for me to keep only the necessary files (I was not able to pick the necessary one) and build on them next?
Thanks in advance

wyldckat · April 14, 2013, 13:34

Hi zania,

"planeWall2D"? That's not one of the official tutorials... is it this one: http://openfoamwiki.net/index.php/Ge..._-_planeWall2D

If I understand your questions correctly, I think I'm only able to answer some of your questions:

Q1) I think the "porous" ones are the ones you're looking for. You can find in the "tutorials" folder cases that are porous-related by running:
Code:
```
find $FOAM_TUTORIALS -iname "*porous*"
```
Q2) laplacianFoam is a very basic solver. And I'm not sure you'll be able to set-up a wall barrier for using with that solver...
Q3) I think you can adjust the parameters in the file "constant/wall/solidThermophysicalProperties". The wall thickness is controlled in "system/topoSetDict" (divides the original mesh into 3 blocks) and "constant/polyMesh/blockMeshDict" (creates the original mesh).
Q5) Like I said in Q1, the porous solvers are probably the ones you need. But I'm not sure of which one of them you need... as for a infinitely thin wall, look for "porous baffles".

Best regards,
Bruno

zania · April 21, 2013, 01:36

Hello Bruno
Thank you for your response.
That is the tutorial.
I’ll check your subjections
Best regards .

March 28, 2013, 06:11	Mass diffusion (ie air or oxygen) through membrane	#1
zania New Member Join Date: Feb 2013 Posts: 15 Rep Power: 13	Hi I am new to OpenFoam and I just managed to run the planeWall2D tutorial (I am not quit sure about all the files). To study: Fluid mass diffusion (ie air or oxygen) through membrane (ie food bag). Next I will have platelets in it (rectangular leaving polymer space about its dimensions around it). Fick's first law is applicable, the diffusive mass flux or the analogue Fourier’s Law of Heat Conduction Heat flux (W/m2) Q1) Is there a solver for mass flux? Q2) What is the appropriate solver (laplasianfoam is only for the second law?) Q3) To start could I use files from the planeWall2D tutorial (leaving out the boundaries near the wall ? Q3.1)Is there a simpler tutorial similar to my case? Q4) In the planeWall2D tutorial if I manage to change the 1)dimensions for mass-diffusivity and concentration 2)The value of high and low concentration 3) the mass-diffusivity, would that be enough for a start? Q5) Would be easier for me to keep only the necessary files (I was not able to pick the necessary one) and build on them next? Thanks in advance

April 14, 2013, 13:34		#2
wyldckat Retired Super Moderator Bruno Santos Join Date: Mar 2009 Location: Lisbon, Portugal Posts: 10,975 Blog Entries: 45 Rep Power: 128	Hi zania, "planeWall2D"? That's not one of the official tutorials... is it this one: http://openfoamwiki.net/index.php/Ge..._-_planeWall2D If I understand your questions correctly, I think I'm only able to answer some of your questions: Q1) I think the "porous" ones are the ones you're looking for. You can find in the "tutorials" folder cases that are porous-related by running: Code: find $FOAM_TUTORIALS -iname "porous" Q2) laplacianFoam is a very basic solver. And I'm not sure you'll be able to set-up a wall barrier for using with that solver... Q3) I think you can adjust the parameters in the file "constant/wall/solidThermophysicalProperties". The wall thickness is controlled in "system/topoSetDict" (divides the original mesh into 3 blocks) and "constant/polyMesh/blockMeshDict" (creates the original mesh). Q5) Like I said in Q1, the porous solvers are probably the ones you need. But I'm not sure of which one of them you need... as for a infinitely thin wall, look for "porous baffles". Best regards, Bruno __________________ OpenFOAM: FAQ \| Getting started Forum: How to get help, to post code/output and forum guide Read this before sending me PM

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April 21, 2013, 01:36		#3
zania New Member Join Date: Feb 2013 Posts: 15 Rep Power: 13	Hello Bruno Thank you for your response. That is the tutorial. I’ll check your subjections Best regards .