Dear Georg,
you are right I forgot that you are using the MPNC. I can not see where
things are going wrong.
What I would propose is to submit a bug-report to our bug tracking
system, if you want I can do that for you. In that way the problem will
dealt with at some point, hopefully soon. If you come up with a
solution, please report it here.
Best regards
Alex
On 13.08.2015 16:38, [email protected] wrote:
Hi Alex,
I attached the relevant pieces of code in the file. Just to make sure
we talk about the same thing: in the mpnc model there are N+M
equations/primary variables for an isothermal system. This gives 5
equations for the 2p3c case and the primary variables are: Sg, pg, and
three fugacities. The pressure and saturation are associated with the
nonlinear complementarity functions (NCP equations), so it seems like
if I set the pressure and saturation on a boundary but do not specify
the mole fractions/fugacities, they are allowed to run wild and the
solution is f***ed up J.
I have a 2p2c fluidsystem at hand and tried it with that as well but
the problem is the same. Seems like there is no easy solution to this.
Georg
*Von:*Dumux [mailto:[email protected]] *Im
Auftrag von *Alexander Kissinger
*Gesendet:* Donnerstag, 13. August 2015 15:44
*An:* DuMuX User Forum
*Betreff:* Re: [DuMuX] Boundary conditions
Dear Georg,
I am not quite sure what causes your problem. Could you send the
implementation of your boundary conditions, i.e. your boudaryTypes()
and your dirichlet() function from your problem?
You could also try the following:
1. Just set the pressure as a Dirichlet condition and make the other
two equations outflow BC.
2. Try it with a 2p2c transport only system (set the third component
to zero everywhere), do you still get unphysical values?
Best regards
Alex
On 08/13/2015 01:56 PM, [email protected]
<mailto:[email protected]> wrote:
Hi Alex,
I tried to do the same thing as in the 1p2coutflowproblem only
with a 2p3c Fluidsystem and the mpnc model. Initially, only the
gas phase is present in the whole domain (Sg=1) and I set
Dirichlet boundary conditions for all primary variables on the
inlet (pg = 1.6 bar, Sg=1 and the mole fractions/fugacities). Then
I set Dirichlet conditions for pressure and saturation on the
outlet (Sg=1, pg=1.5 bar). The Dirichlet conditions are consistent
with the initial conditions. For the component conservation
equations I set outflow conditions on the outlet.
With these boundary conditions, everything should flow from the
inlet to the outlet due to the pressure gradient of the gas phase.
The gas phase composition may change on the way to the outlet due
to reactions: 1 species is consumed, another produced. With the
outflow bc everything that reaches the outlet should be allowed to
leave the domain. Sadly, this is not working.
I get unphysical mole fractions at the outlet (x > 1). Any clues
why this does not work? Is the outflow condition used anywhere in
a 2p-system?
Best regards
Georg
*Von:*Dumux [mailto:[email protected]] *Im
Auftrag von *Alexander Kissinger
*Gesendet:* Freitag, 31. Juli 2015 16:21
*An:* DuMuX User Forum
*Betreff:* Re: [DuMuX] Boundary conditions
Dear Georg,
If I understand correctly this means that whatever is on an
outflow boundary is allowed to flow out or into the system. So if
we assume pure fickian diffusion and the concentration in the
domain is higher than on the boundary stuff will flow out while it
is vice versa if the concentration is lower. If that is the case,
what exactly is the difference to a Dirichlet boundary condition?
As far as I see, with this type of boundary condition I would keep
e.g. a concentration on the boundary constant. Am I correct?
In the case of pure fickian diffusion (no advection i.e. constant
pressure) the concentration at your outflow boundary would
increase until the concentration gradient is zero i.e. no more
flow. The difference between a Dirchlet boundary is that your
concentration at the boundary dof is allowed to change with an
outflow BC.
Consider this example where the outflow boundary is more useful:
1d flow and transport in a tube (model: 1p2c). Left boundary has
Neumann BC with fluid entering at a certain conentration. The
right boundary has a Dirichlet BC for pressure (constant velocity
in the tube) and an outflow boundary for the transported
component. If the BC for the transported component were Dirichlet
the concentration would stay at zero. With the outflow BC the
concentration may increase at the boundary dof and the component
may leave the domain through the advective flux. See also the
test/implicit/1p2coutflowproblem.
Best regards
Alex
On 07/31/2015 02:47 PM, [email protected]
<mailto:[email protected]> wrote:
Dear Alex,
Thanks for your reply!
/“I am not sure if I got you right, you want to have a fixed
Saturation (Dirichlet) for one phase and inject another phase?
In Dumux you can choose the equation that should be replaced
by the Dirichlet condition with the call:
setDirichlet(int pvIdx, int eqIdx)
The equation you choose cannot be assigned to a Neumann BC
anymore.
The rest of the equations can be assigned as Neumann BCs.
Maybe you could list the type of BC you would like to have for
each equation?”
/
I found a workaround to calculate the fluxes at the outlet of
my system, so now I set Dirichlet conditions at the inlet and
solDependentNeumann conditions at the outlet. This should work.
“For the box method the outflow condition uses the gradients
evaluated at the integration point of the boundary face to
calculate the flux out of the domain for the equation you choose.”
If I understand correctly this means that whatever is on an
outflow boundary is allowed to flow out or into the system. So
if we assume pure fickian diffusion and the concentration in
the domain is higher than on the boundary stuff will flow out
while it is vice versa if the concentration is lower. If that
is the case, what exactly is the difference to a Dirichlet
boundary condition? As far as I see, with this type of
boundary condition I would keep e.g. a concentration on the
boundary constant. Am I correct?
Best regards
Georg
*Von:*Dumux [mailto:[email protected]]
*Im Auftrag von *Alexander Kissinger
*Gesendet:* Donnerstag, 30. Juli 2015 08:53
*An:* DuMuX User Forum
*Betreff:* Re: [DuMuX] Boundary conditions
Dear Georg,
I am not sure if I got you right, you want to have a fixed
Saturation (Dirichlet) for one phase and inject another phase?
In Dumux you can choose the equation that should be replaced
by the Dirichlet condition with the call:
setDirichlet(int pvIdx, int eqIdx)
The equation you choose cannot be assigned to a Neumann BC
anymore.
The rest of the equations can be assigned as Neumann BCs.
Maybe you could list the type of BC you would like to have for
each equation?
Secondly, I stumbled across the outflow boundary condition
recently what is the physical idea behind this type of
boundary condition?
For the box method the outflow condition uses the gradients
evaluated at the integration point of the boundary face to
calculate the flux out of the domain for the equation you choose.
Best regards
Alex
On 29.07.2015 16:14, [email protected]
<mailto:[email protected]> wrote:
Hello Dumux,
I am working with the (implicit, box) mpnc-model with a
2p5c fluidsystem and I would like to specify the following
inlet boundary conditions to my system: gas pressure,
saturation and phase composition. This can be done with a
Dirichlet condition and it works fine. But additionally, I
would like to set the gas flux into the model domain
(basically the pressure gradient) which would mean setting
a Neumann boundary condition. Is there a way to do this in
Dumux?
Secondly, I stumbled across the outflow boundary condition
recently what is the physical idea behind this type of
boundary condition?
Thanks for your help!
Georg Futter
——————————————————————————
*German Aerospace Center *(DLR)
Institute of Engineering Thermodynamics | Computational
Electrochemistry | Pfaffenwaldring 38-40 | 70569 Stuttgart
Dipl.-Ing. *Georg Futter* | Ph.D. student
Telefon 0711/6862-8135 | [email protected]
<mailto:[email protected]>
www.DLR.de <http://www.dlr.de/>
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--
Alexander Kissinger
Institut für Wasser- und Umweltsystemmodellierung
Lehrstuhl für Hydromechanik und Hydrosystemmodellierung
Pfaffenwaldring 61
D-70569 Stuttgart
Telefon: +49 (0) 711 685-64729
E-Mail:[email protected]
<mailto:[email protected]>
_______________________________________________
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--
Alexander Kissinger
Institut für Wasser- und Umweltsystemmodellierung
Lehrstuhl für Hydromechanik und Hydrosystemmodellierung
Pfaffenwaldring 61
D-70569 Stuttgart
Telefon: +49 (0) 711 685-64729
E-Mail:[email protected]
<mailto:[email protected]>
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Dumux mailing list
[email protected]
https://listserv.uni-stuttgart.de/mailman/listinfo/dumux
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