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velocity BC for pourous wall (pressure dependendend darcy law)

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Old   May 19, 2017, 10:40
Default velocity BC for pourous wall (pressure dependendend darcy law)
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Dear FOAMers,

i wanna investigate a dead end pipe with some porous areas at the wall.
The porosity variates along the axis, so I will divide the wall in different parts and each part sould get an individual BC depending on the local porosity.
At the inlet of the pipe I will define a pressure BC. Simulation will be steady-state.

My goal is to analyze the averaged leakage for each part of the wall.
I don't wanna simulate the outside of the pipe. I just wanan look at the massflow through the porous wall(s) (which will be treated like an outlet patch).
The fluid is incompressible so i get the massflow with u*rho*area of the wall.

Therefore I'm looking for a velocity BC for porous walls which follows darcys law.

I thought of setting atm pressure at the wall as p-BC.
The velocity BC should calculate the preassure drop between in and outside the pipe (according to the results of the flow field inside) and use a manually given permeability factor k, to calculate the velocity.

u=deltaP*k (normal to the wall)
u=0 (not normal to the wall => there should be shearing)

in the end it is the exact oppposite of the slip condition:
There, the normal component is zero (sliding). It would be a wall (no fluxes can pass) but there is finally no shearing based on the fact that we assume that there are no viscous effect.

I had a look through the provided BC of OpenFOAM but could not find a suitable one for my problem. I also searched in the forum - no success.

May some of you could help me out which one i have to use,
or, in case there isn't such a BC, which one shound be suitable for start programming by myself.

Thanks a lot

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Old   May 29, 2017, 07:53
Default BC pourous wall
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Hi again,

nobody got an idea according this problem?

It would help a lot.

Thank you.
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boundaries condition, darcy's law, permeable wall, porous walls, velocity boundary

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