about conservation of roms

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xmuliuy
Posts: 19
Joined: Fri Nov 02, 2012 3:25 pm
Location: xmu

about conservation of roms

#1 Post by xmuliuy » Tue Dec 18, 2012 8:57 am

Hi everyone,The roms is applied in estuary, and i set some sections in estuary.
but i found the water flux in every section is not the same and some have big difference.
Is there any nonconservation in computering of roms? and is there some options in cppdef.h
needed to defined to ensure the conservation?
thank you .

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kate
Posts: 3704
Joined: Wed Jul 02, 2003 5:29 pm
Location: IMS/UAF, USA

Re: about conservation of roms

#2 Post by kate » Tue Dec 18, 2012 5:38 pm

Sasha Shchepetkin has written at length about the conservation properties in ROMS. I suggest you read his papers for all the details. There is no cppdef option to change it.

I'm not sure what you are expecting, though. Do you have an estuary with channels between the parts? As long as flow is allowed to go from one box to the next, there's no guarantee about conservation in any one box. Perhaps you could explain your issue more clearly?

wangjxmu
Posts: 3
Joined: Tue Nov 18, 2008 5:06 pm
Location: xiamen university

Re: about conservation of roms

#3 Post by wangjxmu » Wed Dec 19, 2012 2:33 am

thank you kate,
In the estuary ,i set some sections from head to mouth. And there is no branch, so the
tidally averaged water flux in the each section should be equal, at least there is almost
the same. But the water flux in the each section is different and from head to mouth the
value decrease strikingly. At the first i suspect the way to computer the flux may be have
some error, but i tride many methods,the result doesn't change. So i suspect the nonconservation
exit in the roms. can you give some advice ? thank you
.I found xxx_VOLCONS(use if Eastern edge mass conservation enforcement) in cppdefs.h , is this
opions can solve this problem?

xmuliuy
Posts: 19
Joined: Fri Nov 02, 2012 3:25 pm
Location: xmu

Re: about conservation of roms

#4 Post by xmuliuy » Wed Dec 19, 2012 2:54 am

thank you kate,
In the estuary ,i set some sections from head to mouth. And there is no branch, so the
tidally averaged water flux in the each section should be equal, at least there is almost
the same. But the water flux in the each section is different and from head to mouth the
value decrease strikingly. At the first i suspect the way to computer the flux may be have
some error, but i tride many methods,the result doesn't change. So i suspect the nonconservation
exit in the roms. can you give some advice ? thank you
.I found xxx_VOLCONS(use if Eastern edge mass conservation enforcement) in cppdefs.h , is this
opions can solve this problem?

this is my cppdef:
# define SOLVE3D
# define UV_COR
# define UV_ADV
# define UV_C4ADVECTION
# define UV_LOGDRAG
# define DJ_GRADPS
# define TS_MPDATA
# define AVERAGES
# define SPHERICAL
# define MASKING
# define SALINITY
# define NONLIN_EOS
# define SPLINES
# define ANA_STFLUX
# define ANA_SSFLUX
# define ANA_SPFLUX
# define ANA_BSFLUX
# define ANA_BTFLUX
# define ANA_BPFLUX
# define TS_PSOURCE
# define UV_PSOURCE
# define SPONGE
# define VISC_GRID
# define DIFF_GRID
# define UV_VIS2
# define TS_DIF2
# define MIX_S_UV
# define MIX_S_TS
# define UV_SMAGORINSKY
# define MY25_MIXING
# ifdef MY25_MIXING
# define N2S2_HORAVG
# define KANTHA_CLAYSON
# define K_C4ADVECTION
# endif
# define RAMP_TIDES
# define SSH_TIDES
# define ADD_FSOBC
# define UV_TIDES
# define ADD_M2OBC


# define EAST_FSCHAPMAN
# define EAST_M2FLATHER
# define EAST_TCLAMPED
# define EAST_M3CLAMPED

# define SOUTH_FSCHAPMAN
# define SOUTH_M2FLATHER
# define SOUTH_TCLAMPED
# define SOUTH_M3CLAMPED

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kate
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Joined: Wed Jul 02, 2003 5:29 pm
Location: IMS/UAF, USA

Re: about conservation of roms

#5 Post by kate » Wed Dec 19, 2012 6:29 pm

Can you show us a picture of your domain?

How are you computing streamflow at the various locations and where are they on the map?

I never use the VOLCONS options because I run with tides and they are inconsistent with VOLCONS.

From your cppdefs:
* I see you have an older version, before the LBC variable.
* I would not use MIX_S_TS, which is asking for cross-isopycnal mixing in the most unphysical way.
* I believe the gang would recommend using MY25 via the GLS_MIXING option instead.

LiuZHQ
Posts: 44
Joined: Mon Apr 06, 2009 5:12 pm
Location: The Hong Kong University of Sci&Tech

Re: about conservation of roms

#6 Post by LiuZHQ » Mon Dec 24, 2012 1:33 am

That *_VOLCON options do nothing to your problem here, because it only conserves the inward and outward volume transport at the open boundaries.

That non-conserved estuary circulation looks strange, and I never see that kind of problem in my idealized estuary cases with buoyancy forcing only. I suggest you double check your program that calculating the "flux" (I supposed it as "volume transport"), and I notice that you included tides into your model. Please make sure to use the residual component in your calculation.

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