[Nek5000-users] Question about method & error

Wed Apr 7 09:43:32 CDT 2010

On Wed, 2010-04-07 at 09:32 -0500, nek5000-users at lists.mcs.anl.gov
wrote:
> I think we can do this problem...  There is support for an internal
> interface (set up originally by Lee Ho) and it appears to still
> be functioning properly.
> 
> You simply specify sigma as desired, in the userbc routine.
> 
> At the liquid interface you need to specify a boundary condition
> "msi"  --- moving surface, interior.
> 
> That is a bit tricky - requires editing the .rea file at present -
> but not really too difficult.
> 
> Let me look a bit further.

Paul,

Great to hear that.  Question; an internal interface has the meaning of
an internal boundary condition at which velocity and temperature, but
not pressure, boundary conditions can be set?  

Since the normal velocity at the interface is set to zero and the
interface completely separates the two fluids, the absolute value of the
pressure in the two fluids is independent in the model I have in mind.
To put in other words, no pressure gradients across the interface exist
in the model.  But I guess that will always be the case in the spectral
element method, as long as the interface is not inside an element.

Cheers,
Frank

> 
> Paul
> 
> 
> 
> On Wed, 7 Apr 2010, nek5000-users at lists.mcs.anl.gov wrote:
> 
> > On Wed, 2010-04-07 at 08:52 -0500, nek5000-users at lists.mcs.anl.gov
> wrote:
> > Frank,
> > 
> > Do you know the surface tension for your case?  Is it a function
> > of temperature?
> 
> Hi Paul,
> 
> The surface tension depends linearly on the temperature, therefore the
> shear stress (tangential to the interface) depends linearly on the
> temperature gradient along (tangential to) the interface.
> 
> Cheers,
> Frank
> 
> > 
> > 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 Gauss–Lobatto–Legendre points), while
> > > > >>> the pressure is located at the Gauss–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 Universität Wien (Technical University of Vienna)
> > > > > Inst. f. Strömungsmechanik und Wärmeübertragung (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
> > > > > 
> > > > > _______________________________________________
> > > > > Nek5000-users mailing list
> > > > > Nek5000-users at lists.mcs.anl.gov
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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 Universität Wien (Technical University of Vienna)
> > > Inst. f. Strömungsmechanik und Wärmeübertragung (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
> > > 
> > > _______________________________________________
> > > Nek5000-users mailing list
> > > Nek5000-users at lists.mcs.anl.gov
> > > https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users
> > > _______________________________________________ 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 Universität Wien (Technical University of Vienna)
> > Inst. f. Strömungsmechanik und Wärmeübertragung (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
> > 
> > _______________________________________________
> > Nek5000-users mailing list
> > Nek5000-users at lists.mcs.anl.gov
> > https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users
> > _______________________________________________ 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 Universität Wien (Technical University of Vienna)
> Inst. f. Strömungsmechanik und Wärmeübertragung (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
> 
> _______________________________________________
> Nek5000-users mailing list
> Nek5000-users at lists.mcs.anl.gov
> https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users
> _______________________________________________ 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 Universität Wien (Technical University of Vienna)
Inst. f. Strömungsmechanik und Wärmeübertragung (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