[MITgcm-support] MITgcm-support Digest, Vol 91, Issue 4

Matthew Mazloff mmazloff at ucsd.edu
Thu Jan 13 13:43:34 EST 2011


Hi Chunyun,

By default the sponge layer will be on both sides.  You will need to  
do a little code modifying to only have the sponge on the west.  It  
may not be too hard though...

-Matt


On Jan 13, 2011, at 10:32 AM, Chun-Yan Zhou wrote:

> 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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>    1. Re: How to use OBCS and add the Sponges layer? (Matthew Mazloff)
>
>
> ----------------------------------------------------------------------
>
> 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";
> DelSp="yes"
>
> 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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