Hi Tri Dat,
On 22.07.2016 18:41, NGO Tri Dat wrote:
Hi Timo,
Thank you for your feedback!
For information, I have also a simulation of 2p flow in another
2d-in-3d DFN.
I considered the behavior of a LNAPL plume in a medium initially
saturated with water, hydrostatic pressure for initial condition
(figure 1 & 2).
A no-flow Neumann BC is prescribed for the top and the bottom faces,
and Dirichlet BC otherwise.
Did you run that with Dumux?
The simulation run correctly (saturation Sn at the final time of
simulation, figure 3) but I got a strange pressure field at a fracture
which is always saturated in water (figure 4).
I’m not sure that this problem is due to boundary condition or the
condition at the intersection between fractures. In addition, the
distribution of fluxes at the intersections between fractures when
using the box method is not very clear for me. Is the mass
conservation at these locations ensured with box method?
Mass conservation should come naturally with the box method at
intersections. As the degrees of freedom are on the intersection you
enforce continuity of pressure.
The fluxes are only computed on the box boundaries with are inside the
elements meeting at the intersection. The box control volume basically
spans over all three (or more)
intersecting elements at the fracture joint. So without doing anything
special the box method should ensure mass conservation here.
If you use cell-centered finite volumes this is different. First, the
gradients in the current dumux master branch would be approximated
incorrectly in a 2d in 3d setting (basically cutting over the edge at an
intersection). Secondly, the intersections with neighboring elements of
the other two (or more) fracture will be handled as independent
intersections. So to ensure the flow is spreading right you would have
to take care about mass conservation yourself. A common approach (at
least for one-phase flow, I'm not sure about 2-phase flow) is a
star-delta type analogy from electrical engineering. The flow (at an
intersection with three or more fractures) from one element to another
then depends on transmissibilities of all participating fractures.
Best wishes,
Timo
Kind regards,
Tri Dat
*De :*Timo Koch [mailto:timo.k...@iws.uni-stuttgart.de]
*Envoyé :* vendredi 22 juillet 2016 17:39
*À :* DuMuX User Forum; NGO Tri Dat
*Objet :* Re: [DuMuX] Convergence problem with FoamGrid 2D3D + Box method
Hi Tri Dat,
Bernd was right and you were probably the first one computing on a 2d
in 3d grid with box.
I looked into it today. The box sub control volume face computed the
wrong normal for dim=2 and dimWorld=3.
I fixed this on a branch feature/ *discrete-fracture-2d3d-test
<https://git.iws.uni-stuttgart.de/dumux-repositories/dumux/commits/feature/discrete-fracture-2d3d-test>*.
This makes everything converge for my little fracture network.
However, something on the boundaries looks still strange (saturation
greater than 1, I tested the 2p model).
I implemented the same problem on our feature/globalvectors branch
that has some major changes and improvements over the current version.
There,
everything looked fine.
We have to look into the issue on the boundaries, so stay tuned.
Best wishes
Timo
On 22.07.2016 14:15, NGO Tri Dat wrote:
Hi Bernd,
You can find, in the attached file, the source files of the test case.
Please let me know if you cannot compile the program.
Thank you for your help.
Kind regards,
Tri Dat
*De :*Dumux [mailto:dumux-boun...@listserv.uni-stuttgart.de] *De
la part de* Bernd Flemisch
*Envoyé :* vendredi 22 juillet 2016 12:09
*À :* DuMuX User Forum
*Objet :* Re: [DuMuX] Convergence problem with FoamGrid 2D3D + Box
method
Hi Tri Dat,
you might be the first one that tries to run Dumux on a
non-manifold 2d-in-3d grid, so I'm not that surprised that you run
into problems. Can you send me the grid, problem, spatialparams
and main files so that we can have a closer look?
Kind regards
Bernd
On 07/22/2016 11:51 AM, NGO Tri Dat wrote:
Hi Dumuxers,
I have a convergence problem with my simulations of 1p flow in
a DFN using FoamGrid (as in the attached file). The fractures
is 2D embedded in a 3D bloc of 100x100x8 m^3. The matrix is
assumed to be impervious. A pressure gradient is prescribed
along the X-axis. Box method and AMG Backend are used.
The error message is:
/Dune reported error: Dune::MathError
[timeIntegration:/work/irlin104_1/ngotr/DUNE/dumux-2.9.0/dumux/implicit/problem.hh:662]:
Newton solver didn't converge after 10 time-step divisions.
dt=9.76563e-14. The solutions of the current and the previous
time steps have been saved to restart files./
Any hints will be greatly appreciated.
Kind regards,
Tri Dat Ngo
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liable for this message./
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