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Posted Fri, 29 Jun 2012 07:35:19 GMT by faby
Hi,
Is there a 3D flow for unconfined aquifer?
faby
Posted Fri, 29 Jun 2012 10:44:14 GMT by faby
Just elaborating my point:
Is the Dupuit-Forchheimer approximation taken into account for unconfined aquifer flow modeling  in FEFLOW?
if yes then is it not a 2D flow??
Posted Mon, 02 Jul 2012 09:41:24 GMT by Denim Umeshkumar Anajwala
Hi Faby,

FEFLOW does not calculate according to Dupuit-Forchheimer approximation, it uses a true 3D approach according to Darcy's law. About the 3D flow for an unconfined aquifer, please see chapter 3 of the reference manual.

Bastian
Posted Fri, 06 Jul 2012 11:00:46 GMT by faby
Hi,
I am still not clear about the equation

pl can u check the doc file I have attached as I was unable to type the equation is this
thankx
faby
Posted Mon, 09 Jul 2012 15:02:30 GMT by Denim Umeshkumar Anajwala
Hi Faby,

I try to extend my explanation. First, let's clarify those equations:

Eq. 3-15 is the horizontal formulation for the unconfined aquifer. It is depth-integrated and yields the (depth-integrated) Darcy velocity, thus it has the unit [m²/s].
The more general formulation is (3-2), however it also contains a buoyancy term. The unit is [m/s], and yields the Darcy velocity.

Eq. 3-16 yields the depth-integrated mass-source term, thus its unit is [kg/m²*s].

The Dupuit approximation is a simplification of 3D settings, practically reducing your first equation to two dimensions, assuming the vertical flow is negligible. The same is valid for any density effects, that's why you don't have any buoyancy term in the 2D formulations (3-10 and 3-15).
Using 3D models in FEFLOW, the Dupuit approximation is not valid. But in 2D horizontal models, these so-called aquifer-averaged-, or horizontal equations are used. The formulations in chapter 3.2 are part of them, so you often find depth-integrated formulas.
Please read chapter 1.5 in the RF for more details.


Bastian

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