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Comparing Analytical solution to comsol Solution

Posted 5 giu 2014, 04:14 GMT-4 Fluid & Heat, Porous Media Flow, Parameters, Variables, & Functions, Results & Visualization 2 Replies

Sepideh Ramezani
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Hello comsolers,

I defined a 2D model in subsurface flow model-using richards' equation for simple rectangle (226*1.2 meter) with imposing upper BC inward flux (because of rainfall) in homogenous, and bottom of rectangle no flow, and for the left and right of the rectangle hydraulic head B.C. with stationary condition. Attached pic1.

Analytical solution that I used is Forchheimer’s equation, attached pic2.
I run this model and I compared the analytical solution with Comsol solution, But it seems that comsol is underestimating the hydraulic conductivity than analytical solution(attached pic3). However, it was expected to have same solution for both method.

Does anybody know where is the problem and what should I do to fit the comsol solution to analytical solution, please?

Thanks in advance for your help.
Sepideh

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2 Replies Last Post 10 giu 2014, 02:30 GMT-4
Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago 7 giu 2014, 16:33 GMT-4
That kind of difference may be caused by different values of the “source” term W between the FEA solution and the analytical model.

Nagi Elabbasi
Veryst Engineering
That kind of difference may be caused by different values of the “source” term W between the FEA solution and the analytical model. Nagi Elabbasi Veryst Engineering
Sepideh Ramezani
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Posted: 1 decade ago 10 giu 2014, 02:30 GMT-4

That kind of difference may be caused by different values of the “source” term W between the FEA solution and the analytical model.

Nagi Elabbasi
Veryst Engineering


Dear Nagi,

In analytical model, "W" is defined as annual average rate of infiltration [LT^-1], but in comsol, I supposed for the upper boundary of rectangle "Inward flux", and I imposed value of Precipitation [LT^-1] as an infiltration rate.
So, is there any possibility that definition of Inward flux is not the same as infiltration rate for the analytical solution? How can I solve this problem?

Thanks in advance for your help
Sepideh
[QUOTE] That kind of difference may be caused by different values of the “source” term W between the FEA solution and the analytical model. Nagi Elabbasi Veryst Engineering [/QUOTE] Dear Nagi, In analytical model, "W" is defined as annual average rate of infiltration [LT^-1], but in comsol, I supposed for the upper boundary of rectangle "Inward flux", and I imposed value of Precipitation [LT^-1] as an infiltration rate. So, is there any possibility that definition of Inward flux is not the same as infiltration rate for the analytical solution? How can I solve this problem? Thanks in advance for your help Sepideh

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