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Setting different diffusivities for two domains (fluid+porous) |
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November 25, 2014, 14:14 |
Setting different diffusivities for two domains (fluid+porous)
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#1 |
New Member
Leonardo
Join Date: Nov 2014
Posts: 27
Rep Power: 12 |
Hi there,
I need some help setting up a CEL expression to define different values of kinematic diffusivity for two different domains: a fluid and a porous domain. I'm aware you can use the inside() function, but I'm not sure how to write it. I tried the script below but it didn't work. 1.58e-5 [cm^2 s^-1] * inside()@flow; 0.46*1.58e-5 [cm^2 s^-1] * inside()@porous Thanks in advance. |
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November 25, 2014, 15:45 |
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#2 |
Senior Member
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I assume you are defining the Kinematic Diffusivity parameter for an Additional Variable, or mass fraction Component
Kinematic Diffusivity = 1.58e-5 [cm^2 s^-1] * ( inside()@flow + 0.46 * inside()@porous) That is all you need to do. I wonder what the 0.46 means. It is not the volume porosity, is it ? |
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November 25, 2014, 15:48 |
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#3 | |
New Member
Leonardo
Join Date: Nov 2014
Posts: 27
Rep Power: 12 |
Quote:
What is the meaning of the asterisk symbol in the CEL syntax? I did a quick check on the documentation and couldn't find much about syntax. And no, it's just the "correction" factor for the permeability at the porous media. |
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November 25, 2014, 16:26 |
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#4 |
Senior Member
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* is for multiplication between two terms in the expression.
Not sure I catch on the "correction factor" for the permeability. There is no permeability in the diffusion terms of the transport equations I have seen. I have only seen the permeability in the drag force term in the momentum equation.. Did you mean porosity ? The only time I have seen permeability into a transport equation is when Darcy's law is substituted into the continuity equation, and a pure diffusion equation for Pressure is obtained. Is that what you are solving for ? |
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November 25, 2014, 16:30 |
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#5 | |
New Member
Leonardo
Join Date: Nov 2014
Posts: 27
Rep Power: 12 |
Quote:
According to the paper I'm basing my simulations on, they estimate the effective diffusivity of ethanol in the porous media using this factor, which indeed happens to include the porosity: D_eff = (porosity)^1.5*D |
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Tags |
cel expression, diffusivity, kinematic diffusivity, porous |
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