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Darcy Law using PDE

Posted 25.08.2013, 22:03 GMT-4 Fluid & Heat, Heat Transfer & Phase Change, Computational Fluid Dynamics (CFD), Porous Media Flow, Modeling Tools & Definitions, Parameters, Variables, & Functions, Studies & Solvers Version 4.3b 3 Replies

Marco Zanoni
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Hi,

I'm trying to implement the Continuity Equation with Darcy law and the Energy equation using a PDE (base package). The Darcy equation in the continuity is u=-(k/mu)*d(p,x) where k is the permeability, mu is the viscosity, and p is the pressure varying with x. However, when I try to implement u in the Energy equation, the term (rho*Cp*u)dT/dx doesn't not work well. I've seen some examples using u.dl, but I'm not sure what is dl. When I try to add it in the equation, the model doesn't recognize dl.

Does anyone has any clue?

Thanks.

Marco
3 Replies Last Post 27.08.2013, 09:11 GMT-4
Suresh Seetharam
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Posted: 1 decade ago 26.08.2013, 04:54 GMT-4
Hi,


In the term, dl.u, dl refers to the model identifier, look for its meaning in the manual. This gives full reference to the variable - so that variables can be used appropriately.

You don't need dl, because this is the default identifier for the in-built Darcy's law in subsurface module. COMSOL would not recognize dl.u because you have not defined it.

With your description, I don't know where you have a problem. But when you set up such equations on your own via PDEs, then verify the individual PDEs with analytical solution or other numerical solutions, then you can be confident to proceed with the coupling.


Suresh
Hi, In the term, dl.u, dl refers to the model identifier, look for its meaning in the manual. This gives full reference to the variable - so that variables can be used appropriately. You don't need dl, because this is the default identifier for the in-built Darcy's law in subsurface module. COMSOL would not recognize dl.u because you have not defined it. With your description, I don't know where you have a problem. But when you set up such equations on your own via PDEs, then verify the individual PDEs with analytical solution or other numerical solutions, then you can be confident to proceed with the coupling. Suresh
Marco Zanoni
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Posted: 1 decade ago 26.08.2013, 11:04 GMT-4
Yes. That was the problem.

Thank you very much. It's working.

Marco

Yes. That was the problem. Thank you very much. It's working. Marco
Marco Zanoni
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Posted: 1 decade ago 27.08.2013, 09:11 GMT-4
Hey guys,

Only one more question. The code is working well, but when I set u=-(k/mu)*d(p,x) instead u=-(k/mu)*px to simulate Darcy's equation, I have noticed different results.

Do you guys know the difference between d(p,x) and px?

Thanks.

Marco
Hey guys, Only one more question. The code is working well, but when I set u=-(k/mu)*d(p,x) instead u=-(k/mu)*px to simulate Darcy's equation, I have noticed different results. Do you guys know the difference between d(p,x) and px? Thanks. Marco

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