Dear Sebastian,
could you please also provide the header files of your test case.
It would help to see the boundary conditions, etc.
Best regards,
Martin
On 14.09.21 08:36, Alexander Sebastian Hogeweg wrote:
Dear Martin,
First of all, thank you again for your time. Now, I built a 1p
(liquid) cornerpoint model to find the origin of the problem. However,
now I am observing a pressure change in the complete structure. The
attached images represent the pressure initially and after the first
timestep (100s). The initialization is done using the hydrostatic
pressure (simpleH2O):
values[0] = globalPos[2] * 1000 * gravity()[2];
The petrophysical properties are defined as homogeneous (k=1mD, phi =
0.2). The structure's thickness is approximately 190m which should
induce a pressure difference of ca. 19 bar along with the structure.
After the first time step, the pressure difference increases to 66bar,
which I do not understand. Do you have any ideas about what is causing
this problem?
Thank you in advance.
Best regards,
Sebastian
*Von:*Martin Schneider <[email protected]>
*Gesendet:* Freitag, 3. September 2021 11:43
*An:* Alexander Sebastian Hogeweg
<[email protected]>;
[email protected]
*Betreff:* Re: AW: [DuMux] Heterogeneous cornerpoint grid - Pressure
drop/increase in scattered cells
Dear Sebastian,
I just checked the tpfa darcylaw:
https://git.iws.uni-stuttgart.de/dumux-repositories/dumux/-/blob/master/dumux/flux/cctpfa/darcyslaw.hh
<https://git.iws.uni-stuttgart.de/dumux-repositories/dumux/-/blob/master/dumux/flux/cctpfa/darcyslaw.hh>
and it seems that you can't use my previous suggestion and simply use
absolute values in the functions of
https://git.iws.uni-stuttgart.de/dumux-repositories/dumux/-/blob/master/dumux/discretization/cellcentered/tpfa/computetransmissibility.hh
<https://git.iws.uni-stuttgart.de/dumux-repositories/dumux/-/blob/master/dumux/discretization/cellcentered/tpfa/computetransmissibility.hh>
because there in the darcylaw we calculate the transbissibility t_j
related to the neighboring element as:
-1.0*computeTpfaTransmissibility(....)
Did you try to change
https://git.iws.uni-stuttgart.de/dumux-repositories/dumux/-/blob/master/dumux/flux/cctpfa/darcyslaw.hh
<https://git.iws.uni-stuttgart.de/dumux-repositories/dumux/-/blob/master/dumux/flux/cctpfa/darcyslaw.hh>
such that all transmissibilities for the flux calculation are positive.
Maybe you could also start setting up a 1p problem and try if it works
there.
Best regards,
Martin
On 03.09.21 11:11, Alexander Sebastian Hogeweg wrote:
Dear Martin,
thank you for the fast response. I followed your recommendations
and changed the cell center location based on the arithmetic mean
(|HACK_CELL_CENTROIDS)|. Here, I am still facing negative values
for the grid block transmissibilities (ti).
Additionally, I use the absolute value for the transmissibilities
leading to positive values. However, the pressure drop/increase in
some cells is still observable.
Do you have other ideas, which could cause this behavior? Thank
you in advance.
Best regards,
Sebastian
*Von:*Martin Schneider <[email protected]>
<mailto:[email protected]>
*Gesendet:* Freitag, 3. September 2021 09:37
*An:* DuMux User Mailing List <[email protected]>
<mailto:[email protected]>; Alexander Sebastian
Hogeweg <[email protected]>
<mailto:[email protected]>
*Betreff:* Re: [DuMux] Heterogeneous cornerpoint grid - Pressure
drop/increase in scattered cells
Dear Sebastian,
for CP-grids it might happen that the centroid is located out of
the cell such that the currently implemented
transmissibility calculation yields negative values.
Did you check if all the transmissibility calculated with the
functions in the following header
https://git.iws.uni-stuttgart.de/dumux-repositories/dumux/-/blob/master/dumux/discretization/cellcentered/tpfa/computetransmissibility.hh
<https://git.iws.uni-stuttgart.de/dumux-repositories/dumux/-/blob/master/dumux/discretization/cellcentered/tpfa/computetransmissibility.hh>
are positive?
I guess you will observe negative values. There are two solutions
to overcome this
1. Try to use another cell center instead of the centroid.
2. Try to use the absolute value of the transmissibility
(corresponds to switching the normal vector of the corresponding face)
I hope this solves your problem.
Best regards,
Martin
On 02.09.21 18:15, Alexander Sebastian Hogeweg wrote:
Hello everyone,
I am facing a problem during the simulation of an underground
gas storage scenario. The used grid is a cornerpoint-grid with
a heterogeneous distribution of permeability and porosity.
Additionally, the structure contains a fault connecting a
lower part of the formation. The used fluid model is 2pnc
(h2on2o2), and the initialization is based on the example
2p_cornerpoint (hydrostatic pressure and pores fully
water-saturated). At the top and bottom of the structure,
Neumann (no-flow) boundaries are defined (Dirichlet at the
sides with initial). In the present status, the molecular
diffusion is deactivated, and additionally, the centroid cell
center location is used.
After the initialization (looks all right), the pressure in
some cells of the lower part increases while neighboring grid
blocks show a lower pressure. Attached you can find some
images showing the problem (Image 1 and 3: t=0; Image 2 and 4:
t =6000s (timestep 8) and the problem file. Other (more
conforming) cornerpoint-grids do not show this behavior.
Overall, I would like to know if somebody else observed a
similar situation and could help me with the problem.
I appreciate any help you can provide, and please let me know
if you need further information.
Best Regards,
Sebastian
Dumux Version: 3.4
Model: 2pnc
Grid type: Cornerpoint
Fluid system: h2on2o2.hh
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