# Permeability Liquid Flow, local coordinates Fault

Hi all,

I have a quick question concerning permeability tensor for 2D surfaces in 3D model using local coorinates.
From what I understood, it is used to give values of the permeabiltiy along the 2D surface (in my case a fault).
I checked the function CFiniteElementStd::CalcCoeffLaplace() in fem_ele_std.cpp but I still haven’t figured everything out.

So for the given material, I can write for example:
#MEDIUM_PROPERTIES
\$GEOMETRY_DIMENSION
2
.
.
.
\$PERMEABILITY_TENSOR
ORTHOTROPIC xx yy

Then to which direction exactly will the values xx and yy be assigned?

Is it also possible to specify the permeability across the surface element?

Thank you in advance.

Best,
Antoine

Hi Antoine,

So for the given material, I can write for example:
#MEDIUM_PROPERTIES
\$GEOMETRY_DIMENSION
2
.
\$PERMEABILITY_TENSOR
ORTHOTROPIC xx yy

Then to which direction exactly will the values xx and yy be assigned?

I'm not quite sure but guess that depends on each element. Current OGS rotates each surface element to XY plane, convert the given local permeability tensor to global one using the rotation matrix. For details of computing a rotation matrix, you can check CElem::FillTransformMatrix() in MSH/msh_elem.cpp

Is it also possible to specify the permeability *across* the surface
element?

No, you need a volume element for it.

···

--
Dr.-Ing. Norihiro Watanabe
Department of Environmental Informatics

Helmholtz-Zentrum für Umweltforschung GmbH - UFZ
Helmholtz Centre for Environmental Research GmbH - UFZ
Permoserstraße 15 / 04318 Leipzig / Germany
Telefon +49 341 235 1806
norihiro.watanabe@ufz.de / www.ufz.de

Sitz der Gesellschaft: Leipzig
Registergericht: Amtsgericht Leipzig, Handelsregister Nr. B 4703
Vorsitzender des Aufsichtsrats: MinDirig Wilfried Kraus
Wissenschaftlicher Geschäftsführer: Prof. Dr. Georg Teutsch
Administrativer Geschäftsführer: N.N.

Thanks for your answer Nori.
I will have a look at that.

Antoine