Hi Lorenzo,
you still have large capillary pressure gradients at the left boundary
at t=600 thus the saturation changes.
You also have them in the initial conditions, so they probably never go
away. Why this is so, depends on your setup. Does it also occur when
your grid is fine from the beginning and you don't have hanging nodes?
What are your criterions for Newton convergence? You seem to be in a
regime of your p_c-S_w curve where a tiny change in pressure makes a
huge difference in saturation. So also numerical error may play a role.
As the boundary conditions are only enforced weakly you can get small
differences very easily.
From a modeling point of view, it's also unclear to me why you need
this wavy initial condition? If it's about producing fingers, which
should be produced by instability, small numerical pertubations in the
boundary conditions should also do the trick. Your initial conditions
produces extremely large pressure gradients in y-direction, too.
I'm not convinced that this is an issue with Dumux.
Best wishes
Timo
On 27.03.19 14:53, lc wrote:
Hello Timo,
I enclose 2 solutions, t = 0 and t = 600 days.
Indeed, I have a saturation profile as IC as you can see at t = 0.h
Best regards,
Lorenzo
On 27.03.2019 16:41, Timo Koch wrote:
Dear Lorenzo,
generally for cell-centered discretizations in Dumux, Dirichlet
boundary conditions are weakly enforced on the boundary. Your first
degree of freedom is half a cell away from the boundary, so it
doesn't necessarily have to be the same as the Dirichlet value.
In order to see if this is actually a mistake or not, we would need
at least a picture of the saturation and pressure fields. If you have
some gradients and varying saturation close to the boundary it's
perfectly normal that the cell values are different than the boundary
values.
For example, does you flow field have finger effects close to the
boundary? That would explain why the profile in the first cell looks
like it does.
Best wishes
Timo
On 27.03.19 14:24, lc wrote:
Hello Dumux team,
We are, finally, in the post-processing phase, aiming at publishing
soon ... but we observed a scaring issue concerning the verification
of the BC at the inlet.
I'm using Dumux 2.12 with the 2p sequential model for a rectangular
domain discretized with a cartesian structured grid with water
inflow (q_w = 0.0001446759 kg / m^2 - s). At the inlet I also impose
a Dirichlet condition on water saturation, s_w = 0.7856 (smax).
The observed issue is visible in the png file
(boundary_condition_t=500_kern1.png):
the horizontal axis in the figure corresponds to the y axis of the
simulation domain (m) and the vertical axis in figure reports the
saturation levels, (s_w).
We see at t = 500 days from the start of the simulation which runs
until 688 days.
So, as we can see, the Dirichlet BC at inlet, s_w = 0.7856 is not
verified. At t = 0, it is ok, but at every later step not any more,
getting a bigger and bigger discrepancy.
May you help me to shed some light on this, please?
I enclose all necessary files to reproduce such behaviour, in case
you have the possiblity to do it.
Kind regards,
Lorenzo
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_______________________________________________________________
Timo Koch phone: +49 711 685 64676
IWS, Universität Stuttgart fax: +49 711 685 60430
Pfaffenwaldring 61 email:timo.k...@iws.uni-stuttgart.de
D-70569 Stuttgart url:www.hydrosys.uni-stuttgart.de
_______________________________________________________________
--
_______________________________________________________________
Timo Koch phone: +49 711 685 64676
IWS, Universität Stuttgart fax: +49 711 685 60430
Pfaffenwaldring 61 email: timo.k...@iws.uni-stuttgart.de
D-70569 Stuttgart url: www.hydrosys.uni-stuttgart.de
_______________________________________________________________
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