[MITgcm-support] OBCs over topography!

[Van Thinh Nguyen]

Hi!

As I told you in last email, I would like to simulate internal waves due
to a tidal flow over a depression Gaussian bump in a open channel at
West/East. I did a lot test cases, I have found that the MITgcm model in
this case is quite sensitive with the vertical mesh density. My water
depth is 120m (80m plat + 40m depth of depression Gausian bump). when I
apply the verical grid delZ=20*6, it worked fine. when I tried to increase
delZ=30*4, it didn't work. I also tried to change hFacMin but it doesn't
help.

Could someone please give a hint to fix this problem?

Thanks so much!

Van Thinh
---------------


On Thu, 20 Oct 2005, Matthew Mazloff wrote:

> Hi Van Thinh!
>
> You can give all cells and the masks will take care of it.  (e.g.
> OB_Ieast=80*-1,OB_Iwest=80*1 is fine)
>
> Other things I have learned:
> 1) You should make the topogrophy flat right at the obcs.  (e.g. make
> the height at (i,j) = (i+1,j) for the western boundary)
> 2) Do not use the CD scheme with obcs
>
> -Matt
>
>
> Van Thinh Nguyen wrote:
>
> >Hi
> >
> >I'm confused how to set up the boundary condition at a OB where a
> >topography intersects with the grid block (please see my figure enclosed).
> >I would like to simulate internal waves due to a tidal flow over a
> >depression Gaussian bump in a channel, which has OBCs at West and East,
> >North & South are closed sides. It looks like the geometry in exp4, the
> >difference is only the bump (my case is depression bump!).
> >Model is 3D, but the Fig. enclosed is a (X,Z) section at middle of bump.
> >
> >At West/East OBs, topography intersects grid block at cell 55 (Z direction
> >with 80 cells). It means:
> >
> >- from free surface to cell 55 is OB
> >- from cell 55 to the bottom is closed
> >
> >In this case, should I define cells (1-55) are OBCs in data.obcs or I can
> >define all cells at West/East are OBCs (with OB_Ieast=80*-1,
> >OB_Iwest=80*1)
> >
> >
> >Could someone please give a hint for this?
> >
> >Thanks so much!
> >
> >Van Thinh
> >
> >------------------------------------------------------------------------
> >
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>