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Posted:
1 decade ago
Dec 22, 2010, 9:07 a.m. EST
in Convection and diffusion eqn for both Comsol Multiphysics and Chemical Engineering modules, velocity is outside of the derivation in the last term, I thing it should be inside the derivation. Is there any special reason for that?
Are you talking about the conservative, non-conservative formulation? in that case, the velocity is out due to having incompressible N-S assumption.
nabla (uc) = u.nabla(c)+c.nabla(u)
and c.nabla(u)=0 (incompressible assumption), so nabla(uc) = u.nabla(c)
--
Comsol 4.1
Ubuntu 10.04.1
[QUOTE]
in Convection and diffusion eqn for both Comsol Multiphysics and Chemical Engineering modules, velocity is outside of the derivation in the last term, I thing it should be inside the derivation. Is there any special reason for that?
[/QUOTE]
Are you talking about the conservative, non-conservative formulation? in that case, the velocity is out due to having incompressible N-S assumption.
nabla (uc) = u.nabla(c)+c.nabla(u)
and c.nabla(u)=0 (incompressible assumption), so nabla(uc) = u.nabla(c)
--
Comsol 4.1
Ubuntu 10.04.1
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Posted:
1 decade ago
Dec 22, 2010, 9:30 a.m. EST
If the fluid is vapor passing through a porous media?
If the fluid is vapor passing through a porous media?
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Posted:
1 decade ago
Dec 22, 2010, 10:03 a.m. EST
Also, in Darcy's flow, I see two del operator before Pressure term , one is out of bracket, the other is in the bracket. while Brinkman eqn. has only one del operator. Why?
Also, in Darcy's flow, I see two del operator before Pressure term , one is out of bracket, the other is in the bracket. while Brinkman eqn. has only one del operator. Why?
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Posted:
1 decade ago
Dec 22, 2010, 3:58 p.m. EST
If the fluid is vapor passing through a porous media?
I don't have access to comsol right now. Can you tell exactly where you mean (re. your first post)?
I would assume if you don't have an incompressible flow you should use the conservative form of c-d.
--
Comsol 4.1
Ubuntu 10.04.1
[QUOTE]
If the fluid is vapor passing through a porous media?
[/QUOTE]
I don't have access to comsol right now. Can you tell exactly where you mean (re. your first post)?
I would assume if you don't have an incompressible flow you should use the conservative form of c-d.
--
Comsol 4.1
Ubuntu 10.04.1
Please login with a confirmed email address before reporting spam
Posted:
1 decade ago
Dec 28, 2010, 10:02 a.m. EST
As Danial pointed out, the default formulation for Transport of Diluted Species is non-conservative. But you can change it through the "Convective term" setting on the Advanced settings section. Switch on Show More Options in the view menu to enable the Advanced setting. See attached screenshot. If you have a fluid that is compressible, you should change it to conservative.
You mention a mass source in a porous medium (due to phase transition). That is another story, use the mass source term Q_br in the Brinkman Equations or Free and Porous media physics interface.
kind regards
Niklas
As Danial pointed out, the default formulation for Transport of Diluted Species is non-conservative. But you can change it through the "Convective term" setting on the Advanced settings section. Switch on Show More Options in the view menu to enable the Advanced setting. See attached screenshot. If you have a fluid that is compressible, you should change it to conservative.
You mention a mass source in a porous medium (due to phase transition). That is another story, use the mass source term Q_br in the Brinkman Equations or Free and Porous media physics interface.
kind regards
Niklas
