[MITgcm-support] open boundaries!

[Stefano Querin]

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
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