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Permeability and Solute Transport in Free and Porous Media
Posted Sep 11, 2015, 9:42 a.m. EDT Fluid & Heat, Computational Fluid Dynamics (CFD), Microfluidics Version 4.2a 1 Reply
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Hi all,
I am trying to model a device that consists of the following:
Top layer: a flowing fluid-filled channel containing solute/molecules of a certain size.
Middle layer: a permeable membrane
Bottom layer: a fluid-filled channel that is originally stationary
My goal is to measure how different flow rates affect transport across the membrane.
I have already built the model and have it working with the Free and Porous Media Flow physics, but have not successfully added solute transport yet.
When characterizing the membrane material, COMSOL asks for a porosity and a permeability; however, permeability seems to be dependent on characteristics of the fluid being used, and I currently have no value for it since the overall goal of my model is to be able to measure how the fluid & solute flow across the membrane. Does anybody know what I might be able to put as an input or how I could determine the permeability for my membrane here?
Also, when setting up the solute transport in my model, I have been trying to work with species transport in porous media, but I have had some trouble with many of the characteristics in the Mobile Fluid, Immobile Solid node, such as Adsorption and Dispersion. Does anybody have tips on how to set up this physics appropriately for my model. I feel a bit stuck and unsure of where to go since I don't know some of these values.
Thank you.
Unfortunately, I can't seem to upload the file.
I am trying to model a device that consists of the following:
Top layer: a flowing fluid-filled channel containing solute/molecules of a certain size.
Middle layer: a permeable membrane
Bottom layer: a fluid-filled channel that is originally stationary
My goal is to measure how different flow rates affect transport across the membrane.
I have already built the model and have it working with the Free and Porous Media Flow physics, but have not successfully added solute transport yet.
When characterizing the membrane material, COMSOL asks for a porosity and a permeability; however, permeability seems to be dependent on characteristics of the fluid being used, and I currently have no value for it since the overall goal of my model is to be able to measure how the fluid & solute flow across the membrane. Does anybody know what I might be able to put as an input or how I could determine the permeability for my membrane here?
Also, when setting up the solute transport in my model, I have been trying to work with species transport in porous media, but I have had some trouble with many of the characteristics in the Mobile Fluid, Immobile Solid node, such as Adsorption and Dispersion. Does anybody have tips on how to set up this physics appropriately for my model. I feel a bit stuck and unsure of where to go since I don't know some of these values.
Thank you.
Unfortunately, I can't seem to upload the file.
1 Reply Last Post Sep 16, 2015, 3:03 p.m. EDT
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Posted:
9 years ago
Hi Elizabeth,
Permeability of porous media are not always easy to measure. If you can do a test where you flow liquid through your membrane and then measure the pressure drop you will be able to estimate the permeability using Darcy's law. If you want an easy estimate, you can use the Carman-Kozeny equation to estimate the permeability using the value of porosity.
Since you are doing the porous media flow using "free and porous media flow" module, i suggest that you try either "transport of dilute species" or "transport of concentrated species".
Have you tried clearing meshes and solutions before you upload?
Regards,
Sri.
Permeability of porous media are not always easy to measure. If you can do a test where you flow liquid through your membrane and then measure the pressure drop you will be able to estimate the permeability using Darcy's law. If you want an easy estimate, you can use the Carman-Kozeny equation to estimate the permeability using the value of porosity.
Since you are doing the porous media flow using "free and porous media flow" module, i suggest that you try either "transport of dilute species" or "transport of concentrated species".
Have you tried clearing meshes and solutions before you upload?
Regards,
Sri.