[mpas-developers] Vector Reconstruction

[Michael Duda]

Hi, Xylar.

Thanks for the quick reply. In SWTC2, the maximum zonal velocity
is around 38 m/s at the equator, so 10 m/s for uReconstructZ does
seem out of place. Just to make sure I understand how to interpret
uReconstruct{X,Y,Z}, these are the components of the velocity
vector in Cartesian space, with the z-axis positive through the
north pole of the sphere, right? I had been testing on a fairly
coarse grid (10242 cells), so that could be a factor; I'll do a
little more testing at higher resolution.

Cheers,
Michael


On Tue, Mar 23, 2010 at 11:41:18AM -0600, Xylar S. Asay-Davis wrote:
> Hi Michael,
> 
> I don't think your attachment made it through.
> 
> I'll take a look at shallow water test case 2 to see what might be the
> problem there. The value of uReconstructZ won't machine zero for a purely
> zonal flow because the reconstruction in its current form will only
> guarantee exact reconstruct of a constant flow in the tangent plane of the
> cell, where as a zonal flow has components slightly out of the tangent
> plane.  In my tests, I was seeing uReconstructZ smaller than uReconstructX
> and uReconstructY by a factor of around 1e-6.
> 
> -Xylar
> 
> 
> > Hi, Xylar.
> >
> > The module looks good to me -- very clean code. The only changes
> > I'd suggest are to the comments at the beginning of the
> > init_reconstruct() routine, and a few changes to indentation, as
> > in the attached module_vector_reconstruction.F.
> >
> > This is most likely a problem in how I'm performing the
> > computation given that both you and Todd have checked the
> > reconstructed vectors, but I'm having trouble getting a zonal and
> > meridional wind from the reconstructed vector in (x,y,z). Even
> > plotting the magnitude of the reconstructed vector, sqrt(x^2 + y^2
> > + z^2), I'm getting some unexpected values in the reconstructed
> > wind speed field for shallow water test case 2 (with alpha=0).
> > Given that we should have purely zonal flow for this test case,
> > I'm suprised to see values in uReconstructZ of order 10. Do either
> > you or Todd have any thoughts or suggestions?
> >
> > Cheers,
> > Michael
> >
> >
> > On Mon, Mar 22, 2010 at 03:30:39PM -0600, Xylar S. Asay-Davis wrote:
> >> Attached is my proposed vector reconstruction code.  I have run several
> >> sanity checks and it seems to work fine.  However, I haven't been able
> >> to
> >> get a full ocean core run with this code.  It is not clear to me if this
> >> has to do with this code or with recent changes that Mark has made to
> >> the
> >> ocean core relating to 3D density.  I'll keep working with Mark to try
> >> to
> >> figure that out, but in the mean time it would be great to have Todd
> >> and/or Michael test out this code to see if it will work for you.
> >>
> >> A registry entry for the coeffs_reconst is required as follows (already
> >> in
> >> the ocean core):
> >> var real    coeffs_reconstruct ( R3 maxEdges nCells ) -
> >> coeffs_reconstruct
> >> - -
> >>
> >> Registry entries for  matrix_reconstruct, normal and  rbf_value are no
> >> longer required by this code.
> >>
> >> -Xylar
> >
> >> _______________________________________________
> >> mpas-developers mailing list
> >> mpas-developers at mailman.ucar.edu
> >> http://mailman.ucar.edu/mailman/listinfo/mpas-developers
> >
> > _______________________________________________
> > mpas-developers mailing list
> > mpas-developers at mailman.ucar.edu
> > http://mailman.ucar.edu/mailman/listinfo/mpas-developers
> >
> 
> 
> ***********************
> Xylar S. Asay-Davis
> E-mail: xylar at lanl.gov
> Phone: (505) 606-0025
> Fax: (505) 665-2659
> CNLS, MS B258
> Los Alamos National Laboratory
> Los Alamos, NM 87545
> ***********************
>