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Question about Permeability Units

Posted Sep 25, 2015, 9:52 a.m. EDT Microfluidics Version 4.2a 2 Replies

Elizabeth Walker
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Hello,

My model contains a porous membrane which I am trying to characterize (permeability and porosity) with physiological values. When characterizing the porous membrane, COMSOL asks for permeability units of m^2; however, in all of the papers that I've looked at to find physiological values, their units of permeability have been cm/s. I've found some other information on converting from hydraulic conductivity (cm/s) to permeability (m^2) but I'm not sure how relevant it is. Does anybody have experience with trying to convert these units and if so, what did you do?

Thank you.
2 Replies Last Post Dec 30, 2016, 4:08 p.m. EST
COMSOL Moderator

Hello Elizabeth Walker

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Prasoon Awasthi
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Posted: 8 years ago Dec 30, 2016, 1:29 p.m. EST
Hi

I saw the Brinkman equation, in which 'k' is the permeability tensor with m^2 unit. If you search permeability tensor in Google, you will get 'Permeability (earth sciences)' wikipedia link, in this m^2 unit is given.
But I am also not cleared about how to convert m/s or cm/s unit to m^2 unit, because both are the permeability unit and both are contradicting also.
Hi I saw the Brinkman equation, in which 'k' is the permeability tensor with m^2 unit. If you search permeability tensor in Google, you will get 'Permeability (earth sciences)' wikipedia link, in this m^2 unit is given. But I am also not cleared about how to convert m/s or cm/s unit to m^2 unit, because both are the permeability unit and both are contradicting also.
Suresh Seetharam
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Posted: 8 years ago Dec 30, 2016, 4:08 p.m. EST
Hi,


Often permeability and hydraulic conductivity are mixed up.

The unit of intrinsic permeability is m^2 and that of conductivity is m/s.

To convert m^2 into m/s you multiply permeability (m^2) with rho*g_const/mu, where rho (kg/m^3) is liquid density, g_const (m/s^2)is the internal variable within comsol for gravity and mu (kg/m/s) is the dynamic viscosity.


Suresh
Hi, Often permeability and hydraulic conductivity are mixed up. The unit of intrinsic permeability is m^2 and that of conductivity is m/s. To convert m^2 into m/s you multiply permeability (m^2) with rho*g_const/mu, where rho (kg/m^3) is liquid density, g_const (m/s^2)is the internal variable within comsol for gravity and mu (kg/m/s) is the dynamic viscosity. Suresh

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