[MITgcm-support] MITgcm-support Digest, Vol 91, Issue 4
Chun-Yan Zhou
c.zhou at dundee.ac.uk
Thu Jan 13 13:32:59 EST 2011
Dear Matthew,
Thanks for your replying. But I still feel confused about the "spongeThickness=15,"
from the above code, how can I know where the sponge layer is? for example, I want put a sponge at the west boundary between i=1 and i=15, the spongeThickness=15. However, Could you tell me how to assure the sponge layer is in the west instead of in the east?
Many thanks!
chunyan
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Today's Topics:
1. Re: How to use OBCS and add the Sponges layer? (Matthew Mazloff)
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Message: 1
Date: Thu, 13 Jan 2011 10:13:41 -0800
From: Matthew Mazloff <mmazloff at ucsd.edu>
To: "mitgcm-support at mitgcm.org" <mitgcm-support at mitgcm.org>
Subject: Re: [MITgcm-support] How to use OBCS and add the Sponges
layer?
Message-ID: <7EC739BF-8D85-4133-8167-764378125731 at ucsd.edu>
Content-Type: text/plain; charset="utf-8"; Format="flowed";
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Hi Chunyan
Mostly fine...although I don't know of anyone who has used Orlanski or
obcs balance succesfully so as a first start you may want to turn
these off and then experiment with them later...so try:
> C This include hooks to the Orlanski Open Boundary Radiation code
> #undef ALLOW_ORLANSKI
>
> C balance barotropic velocity
> #undef ALLOW_OBCS_BALANCE
and then of course
> useOrlanskiEast=.FLASE.,
> useOBCSbalance=.FALSE.,
Also I would use
useOBCSprescribe=.TRUE.,
not sure if "1" works
and also, you give
> OBEuFile = 'OBzonalU.bin',
but you also need to give
> OBWuFile = 'OBzonalU.bin',
As for PARM03 put something like:
&OBCS_PARM03
Urelaxobcsinner=864000.E0,
Urelaxobcsbound=43200.E0,
Vrelaxobcsinner=864000.E0,
Vrelaxobcsbound=43200.E0,
spongeThickness=15,
&
and I would recommend give V,T,and S too -- even if they are trivial
Hope that is everything and not too confusing,
Matt
On Jan 13, 2011, at 1:58 AM, Chun-Yan Zhou wrote:
> Dear all,
>
> I am trying to do quite a simple configuration: The model domain
> covers a continental slope and neighbouring parts of the deep ocean
> and shelf. A barotropic tidal flow into the model domain from the
> east open boundary (2D problem, no y-dependency, no Coriolis). My
> basin is 300km across and I use dx=500m and dz=100*25m (i.e. grid
> dimensions is 600x1x100).
> Furthermore, I want to add a sponge-layer (50 Km width) at the
> lateral boundary of the deep ocean (the west boundary) to absorb the
> baroclinic ?elds.
> I have read the OBCS package in the manual and the examples but
> still can not understand well.
> OBCS_OPTIONS.h
> #include "CPP_OPTIONS.h"
>
> #ifdef ALLOW_OBCS
>
> C Enable individual open boundaries
> #undef ALLOW_OBCS_NORTH
> #undef ALLOW_OBCS_SOUTH
> #define ALLOW_OBCS_EAST
> #define ALLOW_OBCS_WEST
>
> C This include hooks to the Orlanski Open Boundary Radiation code
> #define ALLOW_ORLANSKI
>
> C Enable OB values to be prescribed via external fields that are read
> C from a file
> #define ALLOW_OBCS_PRESCRIBE
>
> C This includes hooks to sponge layer treatment of uvel, vvel
> #define ALLOW_OBCS_SPONGE
>
> C balance barotropic velocity
> #define ALLOW_OBCS_BALANCE
>
> C The following five CPP options are experimental and aim to deal
> C with artifacts due to the low-frequency specification of sea-ice
> C boundary conditions compared to the model forcing frequency.
> C Ice convergence at edges can cause model to blow up. The
> C following CPP option fixes this problem at the expense of less
> C accurate boundary conditions.
> #undef OBCS_SEAICE_AVOID_CONVERGENCE
>
> C Smooth the component of sea-ice velocity perpendicular to the
> edge.
> #undef OBCS_SEAICE_SMOOTH_UVICE_PERP
>
> C Smooth the component of sea ice velocity parallel to the edge.
> #undef OBCS_SEAICE_SMOOTH_UVICE_PAR
>
> C Smooth the tracer sea-ice variables near the edges.
> #undef OBCS_SEAICE_SMOOTH_EDGE
>
> C Compute rather than specify seaice velocities at the edges.
> #undef OBCS_SEAICE_COMPUTE_UVICE
>
> #endif /* ALLOW_OBCS */
> #endif /* OBCS_OPTIONS_H */
>
>
> Data.obcs
> # Open-boundaries
> &OBCS_PARM01
> OB_Ieast=600*1, ( is this right?)
> OB_Iwest=1*1, ( is this right?)
> useOrlanskiEast=.TRUE.,
> useOBCSbalance=.TRUE.,
> useOBCSsponge=.TRUE.,
> #
> useOBCSprescribe=1,
> #
> OBEuFile = 'OBzonalU.bin',
> &
>
> # Orlanski parameters
> &OBCS_PARM02
> Cmax=0.45,
> cVelTimeScale=1000.,
> &
>
> # Sponge-layer parameters
> &OBCS_PARM03
> spongeThickness=100,
> Urelaxobcsinner = long relaxation time scale of your choice,
> Urelaxobcsbound= short relaxation time scale,(is there any method
> to give these two parameters?)
> spongeThickness = # grid points,( how to describe the sponges
> position between (1,1 and 100,1)? )
>
> &
>
> I am appreciate any help/advices; if you need more info let me know.
> Thanks in advance.
> Chunyan
>
>
> Chunyan Zhou
> Division of Civil Engineering
> School of Engineering, Physics and Mathematics
> College of Art, Science and Engineering
> Fulton Building
> University of Dundee
> Dundee DD1 4HN
>
>
>
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>
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