[Nek5000-users] Question about method & error

Thu Apr 8 16:12:00 CDT 2010

On Thu, 2010-04-08 at 15:40 -0500, nek5000-users at lists.mcs.anl.gov
wrote:
> Hi Frank,
> 
> Any idea of BCs for the gas phase?

Hi Paul,

For gas phase, a parabolic profile (in the radial direction) would be
fine.  For the outlet, a convective BC should be OK.

> 
> What about the Reynolds number?

The thermocapillary Reynolds number is 2400.  It is defined as:
sigma1*deltaT/(density*Kinematic_Viscosity**2)
where
sigma1 describes the linear variation of the surface tension coefficient
with temperature (i.e., sigma = sigma0 - sigma1*T)

deltaT --> is the temperature difference between the top and bottom
walls

The density of the gas is 1/1000 of the liquid.  
The Kinematic_Viscosity of the gas is 1/10 of the liquid.  

Cheers,
Frank

> 
> Cheers,
> 
> Paul
> 
> 
> On Thu, 8 Apr 2010, nek5000-users at lists.mcs.anl.gov wrote:
> 
> > On Thu, 2010-04-08 at 06:54 -0500, nek5000-users at lists.mcs.anl.gov
> wrote:
> > Yes - this is correct.
> > 
> > If you can give me a rough idea of dimensions (e.g., minor-major
> > diameters of the bridge), I could knock something out in prenek
> > for you.
> 
> Hi Paul,
> 
> I had to step out for a bit, back for the rest of the night though.
> That would be very kind of you.  The dimensions are: 
> http://tetra.fluid.tuwien.ac.at/fmuldoo/public_html/temp/schematic-3d-liquid-bridge-3.png
> 
> Cheers,
> Frank
> 
> > 
> > Paul
> > 
> > 
> > On Thu, 8 Apr 2010, nek5000-users at lists.mcs.anl.gov wrote:
> > 
> > > Hi Paul,
> > 
> > Thanks very much, that is great to hear.  Is it correct that the latest
> > version is at:?
> > https://svn.mcs.anl.gov/repos/nek5/
> > 
> > I will try to set this up now, first thing being getting the grid (built
> > in Gambit) into the solver.
> > 
> > Cheers,
> > Frank
> > 
> > 
> > On Thu, 2010-04-08 at 04:03 -0500, nek5000-users at lists.mcs.anl.gov
> > wrote:
> > > Frank,
> > > 
> > > I think that the internal fluid interface feature is now working
> > > in the latest svn repo.
> > > 
> > > You will need to identify the bdry between the two fluids with "msi"
> > > on each given face.   Then you would specify surface tension
> > >
> > >        sigma = blah blah blah
> > > 
> > > in userbc, where blah is your desired function.
> > > 
> > > Note that you must also set lx1m, etc. to lx1 in SIZE, and 
> > > IFMVBD, IFSTRS to T in the .rea file.
> > > 
> > > I'll try to help you set this up - but am saturated for the next
> > > 7 days because of mtgs.
> > > 
> > > I've tried a couple of 2D examples and they work sufficiently
> > > well for your purposes (I think - but haven't investigated 
> > > too closely).   I'll try to post some examples in the next 48 hours.
> > > 
> > > Paul
> > > 
> > > 
> > > 
> > > On Wed, 7 Apr 2010, nek5000-users at lists.mcs.anl.gov wrote:
> > > 
> > > >
> > > > Yes - I think that's it.
> > > >
> > > > I'm trying to sort out an issue with the ALE right now...
> > > >
> > > > Paul
> > > >
> > > >
> > > > On Wed, 7 Apr 2010, nek5000-users at lists.mcs.anl.gov wrote:
> > > >
> > > >> On Wed, 2010-04-07 at 09:54 -0500, nek5000-users at lists.mcs.anl.gov
> > > > wrote:
> > > >> Hi Frank,
> > > >> 
> > > >> Actually, the only thing that would be specified at the interface
> > > >> is the surface tension sigma, which would generate a jump in the stress 
> > > >> across the interface.  The fluid and surface would dynamically
> > > >> accommodate to these stresses - and would come to a steady state
> > > >> geometry if that's the what the dynamics dictates.   The temperature
> > > >> would still satisfy the heat equation, and of course you could have
> > > >> different rho-Cp and k in each region.
> > > >> 
> > > >> The code will generate the correct jump in pressure according to the
> > > >> surface tension.   (We can check this with the case of a spherical
> > > >> drop.)
> > > >> 
> > > >> Of course, w/o Lee around we'll have to sort all this out to make
> > > >> certain it does what we expect... but I'm fairly confident that it
> > > >> will.
> > > >> 
> > > >> Paul
> > > >
> > > > Hi Paul,
> > > >
> > > > OK, I think I understand it.  Taking the surface tension coefficient as:
> > > > sigma = sigma0 - sigma1*T
> > > > The size of the jump in the pressure between the liquid and the gas
> > > > would be determined by the size of sigma0 and the surface curvature.
> > > > This would mean then that, assuming an incompressible fluid, the only
> > > > effect of sigma0 would be to define the mean pressure difference between
> > > > the gas and the liquid.  Do this view seem correct?
> > > >
> > > > Cheers,
> > > > Frank
> > > >
> > > >
> > > >> 
> > > >> > 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
> > > >> _______________________________________________
> > > >> 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
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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