Dear DuMuX experts,
I managed to get the boundary values right by modifying darcyslaw.hh as follows
around line 205:
// Obtain inside and outside pressures
//const auto pInside = insideVolVars.pressure(phaseIdx);
//const auto pOutside = outsideVolVars.pressure(phaseIdx);
Scalar pInside, pOutside;
if (!scvf.boundary()) {
// Inside the domain calculate the phase flux using phase
pressures (with pn = pw + pc)
pInside = insideVolVars.pressure(phaseIdx);
pOutside = outsideVolVars.pressure(phaseIdx);
}
else {
// Do not include the contributions from capillary forces for
boundary fluxes
//static_assert( (VolumeVariables::priVarFormulation() ==
TwoPFormulation::p0s1), "darcyslaw.hh: BC implemented for p0s1 formulation
only!");
pInside = insideVolVars.pressure(0); // Set pn := pw, i.e.
pc = 0 for the cells adjacent to the boundary face
pOutside = outsideVolVars.pressure(0);
}
// return flux
return fluxVarsCache.advectionTij()*(pInside - pOutside);
In effect, I am trying to remove the contribution from capillary forces in
Dirichlet ghost cells (there is no porous medium in ghost cells).
However, both the pressure and the saturation field still look weird, see the
attached screenshots. It seems that the water front is not really moving into
the domain.
Your help is greatly appreciated!
Many thanks,
Nikolai
________________________________
From: Dumux <[email protected]> on behalf of Nikolai
Andrianov <[email protected]>
Sent: Wednesday, August 8, 2018 10:23 AM
To: Timo Koch; DuMuX User Forum
Subject: Re: [DuMuX] Non-constant pressure BC for non-zero capillary pressure
Hi Timo,
Thank you for your feedback.
I have updated the README.md of the project with some screenshots and more
detailed description of the problem, please have a look at
https://git.iws.uni-stuttgart.de/andrian/rate-sens-nofrac.
Agree on your points for the cell-centered TPFA scheme, but as you can see at
the README.md, there are order of magnitude difference between the obtained and
expected pressure fields…
Can it be that I am setting pressure BC not on a wetting pressure but some
other quantity?. How can I set the pressure BC on the wetting phase pressure?
Thanks,
Nikolai
From: Timo Koch <[email protected]>
Sent: Tuesday, August 7, 2018 18:41
To: DuMuX User Forum <[email protected]>
Cc: Nikolai Andrianov <[email protected]>
Subject: Re: [DuMuX] Non-constant pressure BC for non-zero capillary pressure
Hi Nikolai,
It's a bit hard to say without seeing the results. Can you provide some
screenshot or something so that it is clear how much the pressure is deviation
where and when (only at the beginning of the simulation)?
One thing that might help: you are using the cell-centered TPFA scheme so
Dirichlet boundary conditions are imposed weakly on the boundary faces. This
means that if you visualize the cell center degrees of freedom, they are not
actually equal to the boundary values, they are rather the values half a cell
away from the boundary. So if you start with a large saturation gradient (from
sw=swr to sw=1 at the boundary) it might take some time until the pressure in
the boundary cell is close to the Dirichlet value.
Best wishes
Timo
On 07.08.2018 18:00, Nikolai Andrianov wrote:
Dear DuMuX experts,
I wonder what can be the reason for the following strange behavior I observe
with a simple waterflooding simulation.
It is a water injection into an oil-saturated 2D block, the fluids are
considered as incompressible. Dirichlet boundary conditions are imposed at left
and right boundaries, whereas there are no-flow at top and bottom boundaries.
Brooks-Corey relative permeabilities and capillary pressure curve are used.
Despite the fact, that the boundary conditions are set for the wetting phase
pressure, the pressure values at the boundary appear to be quite different from
the prescribed ones in case of non-zero capillary pressure. If Pc=0, the
pressure boundary values do take the values prescribed in the problem
formulation.
The project is available at
https://git.iws.uni-stuttgart.de/andrian/rate-sens-nofrac, and I would
appreciate if you could comment on what’s going wrong.
Thanks,
Nikolai
PS: I work with the dumux-course branch.
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_______________________________________________________________
Timo Koch phone: +49 711 685 64676
IWS, Universität Stuttgart fax: +49 711 685 60430
Pfaffenwaldring 61 email:
[email protected]<mailto:[email protected]>
D-70569 Stuttgart url:
www.hydrosys.uni-stuttgart.de<http://www.hydrosys.uni-stuttgart.de>
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