[Nek5000-users] Question about method & error

Wed Apr 7 08:45:54 CDT 2010

Hi Frank,

I think the best way to proceed would be to define an interior
interface and not to use the nek-nek coupling. (This is a judgement
call based on the current state of the codes.)

The pressure shouldn't be much of an issue in this case -- as long
as there is a bit of flexibility then the dimension of the null
space is 1  (or in your case, with outflow bcs, 0).

Let me look into this a bit...

Paul

On Wed, 7 Apr 2010, nek5000-users at lists.mcs.anl.gov wrote:

> On Wed, 2010-04-07 at 06:21 -0500, nek5000-users at lists.mcs.anl.gov
wrote:
> Hi Frank,
> 
> There are several apps driving it.  At present, I think that the
> version is slightly out of step w/ our current repo - but not far.
> The original developer has moved on to a university and to other
> projects, so has not been pushing it since September (though I used
> it extensively in January for some tests).  I've been holding off
> on pushing it further till I had more support.
> 
> If your shared interface has elements on either side that are
> conforming it might also be possible to study the Marangoni
> problem in the std. nek if you use the ALE formulation ---
> If you use a fixed interface we would suffer from the fact
> that the pressure would have a nullspace of dimension 2
> since pressure on either side of the (rigid) interface
> would be determined up to a constant.   This would be 
> difficult for our solvers given that we've designed them
> only to handle the case of an at-most one-dimensional nullspace.

Hi Paul,

The elements on both sides of the interface are conforming.  If the
interface was free to move, but had a very high surface tension, high
enough that it was essentially fixed, then perhaps that could work?  But
then there could be problems with ill-conditioning with a very high
surface tension.

> 
> How complex is your domain?

Not very.  It consists of a liquid suspended (due to surface tension)
between two metal posts.  The liquid is surrounded by a gas flow. 
http://tetra.fluid.tuwien.ac.at/fmuldoo/public_html/temp/schematic-3d-liquid-bridge-2.png

I have gridded it using a block structured grid of 9 blocks, five in the
liquid region and four in the gas. The terminology for the whole problem
is a "liquid bridge".

Cheers,
Frank

> 
> Paul
> 
> On Wed, 7 Apr 2010, nek5000-users at lists.mcs.anl.gov wrote:
> 
> > On Tue, 2010-04-06 at 12:58 +0200, nek5000-users at lists.mcs.anl.gov
> wrote:
> > NEK-NEK stands for the coupling of two independent NEK instances. Unfortunately this is still an experimental feature but if you're interested in we can set up something for you.
> 
> Hello Stefan,
> 
> If I can make up a grid, is getting an instance of the NEK-NEK
> capability working something you are willing to work with me to get
> running?  Couple of questions: How experimental is the NEK-NEK
> capability?  And is there a specific application or class of problems
> driving it?
> 
> Cheers,
> Frank
> 
> > 
> > Stefan
> > 
> > 
> > On Apr 6, 2010, at 12:54 PM, nek5000-users at lists.mcs.anl.gov wrote:
> > 
> > > Hello Stefan,
> > > 
> > > Thanks, that fixed it.  By the way, (from your earlier email) what does
> > > NEK-NEK stand for?
> > > 
> > > Cheers,
> > > Frank
> > > 
> > > On Tue, 2010-04-06 at 12:45 +0200, nek5000-users at lists.mcs.anl.gov
> > > wrote:
> > >> Hi Frank,
> > >> 
> > >> On Apr 6, 2010, at 12:32 PM, nek5000-users at lists.mcs.anl.gov wrote:
> > >>> Am I correct in understanding that all components of velocity are
> > >>> stored at the same locations (the Gaussâ€“Lobattoâ€“Legendre points), while
> > >>> the pressure is located at the Gaussâ€“Legendre points?  This being in
> > >>> contrast to a MAC type staggered grid, where each velocity component
> > >>> resides at different spatial locations.
> > >>> 
> > >> Yes that's correct!  In NEK two different methods are implemented:
> > >> 
> > >> PN/PN: (v,p) are defined on the GLL points
> > >> PN/PN-2: v is defined on the GLL points and p on the GL points
> > >> 
> > >> 
> > >>> VisIt could not read from the file
> > >>> "/home/fmuldoo/nek5_svn/examples/turbChannel-1/turbChannel0.f0001".
> > >>> 
> > >>> The generated error message was:
> > >>> 
> > >>> There was an error
> > >>> opening /home/fmuldoo/nek5_svn/examples/turbChannel-1/turbChannel0.f0001. It may be an invalid file.  VisIt tried using the following file format readers to open the file: Silo
> > >>> 
> > >>> When using the following metadata file:
> > >>> 
> > >>> NEK5000
> > >>> version: 1.0
> > >>> filetemplate:  turbChannel0.f%04d
> > >>> firsttimestep: 1
> > >>> numtimesteps: 1
> > >> It seems like you're using a wrong filetemplate. Please try again with:
> > >> filetemplate:  turbChannel%01d.f%04d
> > >> 
> > >> 
> > >> #Stefan
> > >> 
> > >> _______________________________________________
> > >> Nek5000-users mailing list
> > >> Nek5000-users at lists.mcs.anl.gov
> > >> https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users
> > > -- 
> > > Frank Herbert Muldoon, Ph.D. Mechanical Engineering
> > > Technische UniversitÃ¤t Wien (Technical University of Vienna)
> > > Inst. f. StrÃ¶mungsmechanik und WÃ¤rmeÃ¼bertragung (Institute of Fluid
> > > Mechanics and Heat Transfer)
> > > Resselgasse 3
> > > 1040 Wien
> > > Tel: +4315880132232
> > > Fax: +4315880132299 
> > > Cell:+436765203470
> > > fmuldoo (skype)
> > > http://tetra.fluid.tuwien.ac.at/fmuldoo/public_html/webpage/frank-muldoon.html
> > > 
> > > _______________________________________________
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> > > Nek5000-users at lists.mcs.anl.gov
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> > 
> > _______________________________________________
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> -- 
> Frank Herbert Muldoon, Ph.D. Mechanical Engineering
> Technische UniversitÃ¤t Wien (Technical University of Vienna)
> Inst. f. StrÃ¶mungsmechanik und WÃ¤rmeÃ¼bertragung (Institute of Fluid
> Mechanics and Heat Transfer)
> Resselgasse 3
> 1040 Wien
> Tel: +4315880132232
> Fax: +4315880132299 
> Cell:+436765203470
> fmuldoo (skype)
> http://tetra.fluid.tuwien.ac.at/fmuldoo/public_html/webpage/frank-muldoon.html
> 
> _______________________________________________
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> _______________________________________________ Nek5000-users mailing list Nek5000-users at lists.mcs.anl.gov https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users
-- 
Frank Herbert Muldoon, Ph.D. Mechanical Engineering
Technische UniversitÃ¤t Wien (Technical University of Vienna)
Inst. f. StrÃ¶mungsmechanik und WÃ¤rmeÃ¼bertragung (Institute of Fluid
Mechanics and Heat Transfer)
Resselgasse 3
1040 Wien
Tel: +4315880132232
Fax: +4315880132299 
Cell:+436765203470
fmuldoo (skype)
http://tetra.fluid.tuwien.ac.at/fmuldoo/public_html/webpage/frank-muldoon.html

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