[MITgcm-support] open boundaries!

[Van Thinh Nguyen]

Hi Stefano and Patrick,

I took a look on MITgcm Support Archives to find how to set up OBCs,
however I still confuse in setting up some parameters.

My test case is almost the same as exp4:

Flow in a channel over a bump with
- north and south boundaries are walls
- west & east are OBs
I would like to set the tidal forcing at west OB with velocity component
U=Uo*cos(omega*t). (Uo=0.025; omega=2*pi/43200)

Could you please give a hint how can I set these inputs?

Thanks so much for your helps,

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


On Mon, 26 Sep 2005, Stefano Querin wrote:

> Hi Van-Thinh,
> maybe the best thing you can do is to take a look to the files in the CVS
> repository (or directly in your /pkg/obcs folder if you have a recent
> version of the code). Some routines have short and useful comments that help
> the user in the preliminar obcs tests.
> Basically (and in very few words), you can impose:
> - constant OBCs (obcs_calc.F sets u, v, w and eta to zero, and T, S to tRef
> and sRef);
> - radiating (passive) OBCs for momentum and tracers following Orlanski (see
> Orlanski, 1976);
> - time varying (active) OBCs using the obcs package (set
> useOBCSprescribe=.TRUE.,) together with exf and cal.
>
> You can also define a sponge (or better, nudging?) layer on the OB (setting
> useOBCSsponge=.TRUE., sponge thickness and relaxation parameters) and/or
> prescribe the net flow across the OB using the useOBCSbalance option.
>
> A useful example is in:
>
> http://mitgcm.org/cgi-bin/viewcvs.cgi/MITgcm_contrib/heimbach/obcs_prescribe/
>
> As the old obcs/README said, happy open-boundarying!
>
> Cheers,
>
> Stefano
>
>
> ----- Original Message -----
> From: "Van Thinh Nguyen" <vtnguyen at moisie.math.uwaterloo.ca>
> To: <mitgcm-support at mitgcm.org>
> Sent: Monday, September 26, 2005 6:26 PM
> Subject: [MITgcm-support] open boundaries!
>
>
> >
> > Dear MITgcm-supporters & users,
> >
> > Could someone please explain for me more detail about how to set up an
> > open boundary conditions. For instance, in exp4:
> >
> > when we set in data.obcs:
> >
> > "OB_Jnorth=80*-1" to define a face where OB is appied, however I still
> > don't know which boundary condition is appied here (Neumann?).
> >
> > And what is the "useOrlanski" in OB option?
> >
> > There are probably some docu around in MITgcm users' manuals (I actually
> > took a look but haven't found), if someone know please give me a hint?
> >
> > Thanks a lot!
> >
> > Van Thinh
> > _______________________________________________
> > MITgcm-support mailing list
> > MITgcm-support at mitgcm.org
> > http://mitgcm.org/mailman/listinfo/mitgcm-support
> >
>
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