[Nek5000-users] Marangoni effect

[nek5000-users at lists.mcs.anl.gov]

Hello Paul,

Thanks for the help here.  I am currently trying to run some test cases,
specifically the one "turbChannel".  I am getting errors:

               WARNING: DIV(V)-QTL too large!


The ALE free-surface formulation is something that we are very
interested using in the next step of our modeling.

Cheers,
Frank

On Tue, 2010-04-06 at 06:58 -0500, nek5000-users at lists.mcs.anl.gov
wrote:
> Hi Frank,
> 
> There should be a way to impose the shear, which corresponds to an
> inhomogeneous Neumann condition in the stress-formulation.
> 
> The precise values would be supplied by the user through userbc --
> generally it's a good idea to compute the quantity in userchk and
> save this to an array, then de-reference the array values in userbc(),
> which is called once per gridpoint per timestep (as opposed to
> once per timestep, like userchk).
> 
> I'll check to see if I can determine the correct bc flag to enable
> this condition.   To be sure, you will need to use the Pn-Pn-2
> formulation, with the stress condition turned on.
> 
> Unit normal and unit tangent vectors are available for each element
> surface, and routines that allow computations with volume-based and
> surface-based arrays abound (e.g., compute dot-product of grad T with
> unit normal, where former array is volume-based and latter is surface
> based).
> 
> 
> 
> Note that Nek supporst an ALE free-surface formulation - just fyi
> if this is relevant to your problem.
> 
> Paul
> 
> 
> On Tue, 6 Apr 2010, nek5000-users at lists.mcs.anl.gov wrote:
> 
> > Hello all,
> 
> Is there a boundary condition that allows one to specify the shear
> stress vector in terms of the temperature gradient along the boundary?
> The boundary in question is a curved surface in 3D.
> 
> If not, do y'all think that is this something that could be done without
> extreme difficulty?
> 
> Cheers,
> Frank
> 
> -- 
> 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
> 
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-- 
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