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About coupling Richards Equation

Posted 30 oct. 2012, 09:07 UTC−4 Porous Media Flow Version 4.3 3 Replies

Wei Shao
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Dear Sir:
I want to coupling two Richards equation exactly on the same Geometry, to represent two different subsurface flow with different velocity, and define a function as a source sink term depend on the difference of pressure head to calculate the exchange of water. I can let two Richards equation calculated simultaneously, but I can not couple them and calculate the exchange, can you tell me how to couple 2 Richards equations and calculate the water exchange between them?
another question is, it is seems that ComSol is not very stable when solving Richards equation, especially when initial saturation and pressure head is very low, I can see the obvious overshot which is caused by numerical problem, can you tell me how to solve this problem?
3 Replies Last Post 22 sept. 2016, 06:49 UTC−4
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 30 oct. 2012, 09:21 UTC−4
Hi

this is not really my pot of tea ;) other here are better, but as I just checked 3 cases within an hour that have issues with mesh density in critical regions, I was woundering if this is not also partly your issue (concening the stability) diffusion equations, diffusivity, mesh scale length and i.e. time stepping require some coordination to get good reliable results.

if you have twosimilar physiscs on the same domain, you need to couple them correctly, else there interaction will not work

--
Good luck
Ivar
Hi this is not really my pot of tea ;) other here are better, but as I just checked 3 cases within an hour that have issues with mesh density in critical regions, I was woundering if this is not also partly your issue (concening the stability) diffusion equations, diffusivity, mesh scale length and i.e. time stepping require some coordination to get good reliable results. if you have twosimilar physiscs on the same domain, you need to couple them correctly, else there interaction will not work -- Good luck Ivar
Wei Shao
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Posted: 1 decade ago 30 oct. 2012, 09:26 UTC−4
if you have twosimilar physiscs on the same domain, you need to couple them correctly, else there interaction will not work


Dear Sir:
The numerical oscillation can be relieved by refine the mesh. Thank you very much!!That is exactly my problem,

I have two same physics and equation exactly on the same domain, and I need add the exchange as a source or sink term to calculate the interaction.

the exchange can be done by define a exchange function in the source/sink term. It is works, Thank you.
if you have twosimilar physiscs on the same domain, you need to couple them correctly, else there interaction will not work Dear Sir: The numerical oscillation can be relieved by refine the mesh. Thank you very much!!That is exactly my problem, I have two same physics and equation exactly on the same domain, and I need add the exchange as a source or sink term to calculate the interaction. the exchange can be done by define a exchange function in the source/sink term. It is works, Thank you.
Amine Menad
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Posted: 8 years ago 22 sept. 2016, 06:49 UTC−4
thank you
thank you

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