[MITgcm-devel] Hack to increase mixing near bottom/surface

[Jean-Michel Campin]

Hi Dan,

I've just made a tar file with code and input files that I used for
"p15" test (linearDrag & pCellMix_select= 2),
It's there: http://mitgcm.org/~jmc/pCellMix/visc_2d_setup.tgz

Let me know is something is not clear.

Cheers,
Jean-Michel

On Sat, Apr 18, 2015 at 08:43:16PM +0100, Daniel Goldberg wrote:
> Hi J-M and Martin --
> 
> Jean-Michel, I am following up on the hack to increase mixing, and am now
> trying to reproduce your results shown below so that I can apply the hack
> to SHELFICE and investigate wet-point averaging in the ustar calculation.
> 
> I use the latest version of your modified source files and PCELL_MIX.h. I
> tried to reverse engineer the description and figures you show but I am
> unable to do so -- I show the results corresponding to type 1 test here
> http://www.geos.ed.ac.uk/~dgoldber/pcell_mix_bottom_test/figs/
> w_p02 corresponds to your p02. Vertical velocity can be seen elsewhere than
> the edge of the step but is still very large in the column at the the edge
> of each step.
> 
> I am not sure if this is because I have not made the same setup as you, I
> did not see your input file so I had to guess at some things -- my input
> folder is here
> http://www.geos.ed.ac.uk/~dgoldber/pcell_mix_bottom_test/input/
> and my guess at obcs velocity (i did not see your magnitude?) is here
> http://www.geos.ed.ac.uk/~dgoldber/pcell_mix_bottom_test/figs/obcs_u.jpg
> 
> Or alternatively do you still have your input folder? This would be easiest
> to see what I did wrong..
> 
> Thanks very much
> Dan
> 
> 
> On Fri, Jan 16, 2015 at 7:05 PM, Jean-Michel Campin <jmc at ocean.mit.edu>
> wrote:
> 
> > Hi Dan and Martin,
> >
> > I made some simple test with a hack to increase mixing near above bottom
> > and/or
> > below surface when the bottom/surface grid cell is thin (small hFac).
> >
> > I put some files here: http://mitgcm.org/~jmc/pCellMix/
> > with some documentation in file "pCellMix.notes"
> >  and some plots from my simple test.
> >
> > the hack: it should move to the main code at some point, but
> > 1) need more tests (and feedback)
> > 2) it involves changing more S/R (> 7 but only 2 right now) since it
> >  needs to be pushed where vertical diffusion and viscosity are applied:
> >  ( mom_u/v_implicit_r.F mom_u/v_rviscflux.F
> >    impldiff.F gad_diff_r.F gad_implicit_r.F )
> >  and passing more arguments to these S/R (-> also changing the calling S/R)
> >
> > Some remarks:
> > 1) we should probably always use selectBotDragQuadr=1 or 2 instead of the
> > original
> >   discretisation (selectBotDragQuadr=0), see
> > http://mitgcm.org/~jmc/pCellMix/fig_wt4.ps
> > 2) accounting for partial cell in the interior (interViscAr_pCell=T,
> >   interDiffKr_pCell=T) is safe when using implicit visc/diff ;
> >   but also accounting for hFac in bottom friction (bottomVisc_pCell=T) when
> >   using no-slip-bottom=T can be unstable; and we don't have code for
> > implicit
> >   bottom friction + it would not work with present solve_for_pressure code.
> >
> > Regarding how this could be use with pkg/shelfice (to avoid using
> > SHELFICEboundaryLayer):
> > 1) in isomip test experiment, no_slip_shelfice=F and this is good,
> > otherwise
> >    the velocity below ice-shelf is strongly reduced when hFac is small
> > (and it's
> >    physical) and make the melt-rate very dependent on hFac.
> > 2) using a type of quadratic drag: the equivalent of selectBotDragQuadr >
> > 0 is not
> >    coded in shelfice_u/v_drag.F but should not be hard (+ I added the new
> > argument)
> > 3) might need to test different averaging (e.g. wet-point) of the velocity
> >    to the grid-cell center (in shelfice_thermodynamics.F)
> >    I don't know if there is a diagnostic for this (but could be useful)
> > 4) would be interesting to try SHELFICEboundaryLayer=F and
> > pCellMix_select=10 ;
> >
> > Cheers,
> > Jean-Michel
> >
> > _______________________________________________
> > MITgcm-devel mailing list
> > MITgcm-devel at mitgcm.org
> > http://mitgcm.org/mailman/listinfo/mitgcm-devel
> >
> 
> 
> 
> -- 
> 
> Daniel Goldberg, PhD
> Lecturer in Glaciology
> School of Geosciences, University of Edinburgh
> Geography Building, Drummond Street, Edinburgh EH8 9XP
> 
> 
> em: D <dgoldber at mit.edu>an.Goldberg at ed.ac.uk
> web: http://ocean.mit.edu/~dgoldberg

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