On 04.04.19 10:05, Johannes Koestel wrote:
Hej Bernd,
Thanks for the quick reply.
Ah, I am wondering about the second case, of course.
I am a bit unsure about the terminology. I was referring to what is
referred to as 2p2c in the attached paper.
(no, there will not be roots in the models I want to run).
The Stokes equation on an explicitly resolved pore geometry would be
ultimate goal, especially if it could be coupled to a
Darcy-domain. But I had the impression that it is still unrealistic
without true supercomputers (with whatever software).
As for setting up Dumux and trying out one time step, I surely would
appreciate help. Thank you.
I will take the Dumux short course at the Interpore and plan to try it
out after that. I probably will again contact the forum by then.
For now, I only need a rough estimate on what kind of discretization I
could run Dumux with on the specified computer.
It would be for a grant application.
It is planned to gather tomographies on water flow in soil. These 3-D
image will be approximately 250 megavoxels large (a cylinder with 600
vx diameter and 900 vx height).
Due to the dynamic meshing, the number of elements depends on the
permeability structures, saturations and potential fields, right?
OK.. so it is not so easy to estimate how much computation time it
would need, correct?
Hi John,
which spatial size do your tomography images cover? Will the resolution
be above or below an REV-scale. That will also determine how many cells
you want to have. And you are right, when you track a front, e.g., with
adaptive grid refinement you may significantly reduce the number of
cells. Also how detailed will your permeability/porosity data be?
Anyway, just to come up with a very rough estimate: if you want 250 Mio
cells at 40 cores, that's gonna be 6Mio cells per core. It could easily
take 10-30min for a time step (fully-implicit, Newton), which would mean
one simulation would probably be in the order of weeks. You might also
get memory problems at that size, because we currently don't implement
matrix-free solvers.
Do you really need the same resolution in the model as in the tomography
image? I.e. will there be interesting structures that are so small that
this resolution is needed to capture the relevant effects?
And to be fully honest with you, we don't have too much experience with
simulations at that size.
Cheers,
Timo
But if I would reduce the resolution by a factor 2, i.e. app. 43
megavoxels (300 vx diameter and 450 height), this would put me on the
safe side?
Cheers and thanks,
/John
*From:* Flemisch, Bernd <[email protected]>
*Sent:* Thursday, April 4, 2019 8:59 AM
*To:* [email protected]
*Cc:* Johannes Koestel <[email protected]>
*Subject:* AW: system requirements for Dumux with 2C2P in 3-D
Hi Johannes,
it sounds like you want to solve (Navier)Stokes on an explicitly
resolved pore geometry? Or do you want to use Darcy's law without
resolving the pores but using saturation, permeability, porosity and
so on? The first case would currently be impossible with Dumux since
we don't have a two-phase Stokes model. The second case would be
feasible, we could look at how much time it needs for one time step
and then estimate the overall cost.
Kind regards
Bernd
--
_______________________________________________________________
Bernd Flemisch phone: +49 711 685 69162
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>
_______________________________________________________________
------------------------------------------------------------------------
*Von:*Dumux <[email protected]
<mailto:[email protected]>> im Auftrag von
Johannes Koestel <[email protected] <mailto:[email protected]>>
*Gesendet:* Mittwoch, 3. April 2019 14:59:24
*An:* [email protected]
<mailto:[email protected]>
*Betreff:* [DuMuX] system requirements for Dumux with 2C2P in 3-D
Hej,
I am interested in using Dumux to run flow and transport simulations
in soil with 3-D resolution.
Could you help me with getting an idea about the computational demands?
More specifically:
How much days would I approximately need to …
.. model water and air flows (2c2p) under transient conditions in soil
(without fissures or similar) ..
.. and a perfectly conservative tracer transport with it (say D2O) ..
.. in a 3-D domain with 250 megavoxels …
.. using an Intel Xeon with 40 CPUs @2.4 GHz, 128 GB RAM?
Will it be hours, days or years? Will it run at all on such a system?
Thanks a lot for your help,
Cheers from Sweden,
/John
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_______________________________________________________________
Timo Koch phone: +49 711 685 64676
IWS, Universität Stuttgart fax: +49 711 685 60430
Pfaffenwaldring 61 email: [email protected]
D-70569 Stuttgart url: www.hydrosys.uni-stuttgart.de
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