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Why is Storage model in Darcy's Law time dependent?

Posted Jan 6, 2016, 12:43 a.m. EST Fluid & Heat Version 5.1 4 Replies

Tianhang Bai
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Dear all,

A simple square using Darcys Law. If I use the default "fluid and matrix properties" and make all the material properties as CONSTANTS, the result is static even if I use time dependent solver, and this can be explained from the governing equations. However, if I use "storage model" instead, make all properties CONSTANTS, including S, the result is now time dependent, which is contradictory to the governing equations (see attached figure). When density and porosity are constants, the time derivative term should be zero, which is not time dependent. Can anybody tell me why does this happen? Thanks a lot.

Regards,
Albert
4 Replies Last Post Jan 14, 2016, 7:54 a.m. EST
Xu Yi
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Posted: 9 years ago Jan 13, 2016, 2:54 a.m. EST
In the governing equations，the first eqation is the default "fluid and matrix properties", while the second one does represent the "storage model". The "storage model" is time dependent when S is not defined as zero.
In the governing equations，the first eqation is the default "fluid and matrix properties", while the second one does represent the "storage model". The "storage model" is time dependent when S is not defined as zero.
Tianhang Bai
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Posted: 9 years ago Jan 13, 2016, 6:15 p.m. EST

In the governing equations，the first eqation is the default "fluid and matrix properties", while the second one does represent the "storage model". The "storage model" is time dependent when S is not defined as zero.


Thank you for your reply, Xu. I am still confused. Look at the left side of the second equation, if porosity and density is constant, which is the case in my model, should not the left side equals to zero?

Hope to hear from you soon. Thanks.

Regards,
Tianhang
[QUOTE] In the governing equations，the first eqation is the default "fluid and matrix properties", while the second one does represent the "storage model". The "storage model" is time dependent when S is not defined as zero. [/QUOTE] Thank you for your reply, Xu. I am still confused. Look at the left side of the second equation, if porosity and density is constant, which is the case in my model, should not the left side equals to zero? Hope to hear from you soon. Thanks. Regards, Tianhang
Xu Yi
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Posted: 9 years ago Jan 14, 2016, 6:57 a.m. EST
The "storage model" use the right side of of the second equation instead of the left one. The parameter "S" repesents the storage coefficient (SI unit: 1/Pa).
The governing equation of the "storage model" takes the following form

this equation is independend of porosity.
The "storage model" use the right side of of the second equation instead of the left one. The parameter "S" repesents the storage coefficient (SI unit: 1/Pa). The governing equation of the "storage model" takes the following form this equation is independend of porosity.

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Tianhang Bai
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Posted: 9 years ago Jan 14, 2016, 7:54 a.m. EST
Thank you very much for the explanation, Xu.

Thank you very much for the explanation, Xu.

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