blowing up on nested grid

General scientific issues regarding ROMS

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jitraporn13
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blowing up on nested grid

#1 Post by jitraporn13 » Sun Aug 12, 2018 6:50 am

Dear All,

I’m trying to run nested grid, It blows out since the beginning
I noticed on DZmax and courant number on Grid02:
Minimum X-grid spacing, DXmin = 1.00000000E-40 km
Maximum X-grid spacing, DXmax = 5.12482819E+00 km
Minimum Y-grid spacing, DYmin = 1.00000000E-40 km
Maximum Y-grid spacing, DYmax = 5.01111003E+00 km
Minimum Z-grid spacing, DZmin = 5.60947682E-02 m
Maximum Z-grid spacing, DZmax = 4.64003949E+35 m

Minimum barotropic Courant Number = 1.23681706E-03
Maximum barotropic Courant Number = 1.40071410E+56
Maximum Coriolis Courant Number = 1.00000000E+37

When I checked Grid02 by itself. It works well. Please give me some suggestion.

Bests,
Jitraporn

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arango
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Re: blowing up on nested grid

#2 Post by arango » Sun Aug 12, 2018 3:36 pm

The information is in the front of you. If you don't understand that information, you have homework to do before running ROMS. Look the large and a small numbers. Check your grid files. (DXmin, DYmin) cannot be zero!!! It is a trillion times smaller than the scales of electrons... I am sure that it is not what you are modeling.

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wilkin
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Re: blowing up on nested grid

#3 Post by wilkin » Mon Aug 13, 2018 2:14 pm

When I checked Grid02 by itself. It works well. Please give me some suggestion.
By this do you mean you get the same extreme DXmin, DYmin and DZmax yet it runs?

If so, then the issues you are having (this is a guess) may be associated with a poor match of land/sea mask in the contact points region. If you have "wet" points in grid 2 that map to "dry" points in grid 1, the initial value of zeta in the contact points region may be a special value (1E+35) from the initial conditions file which could explain your extreme DZmax of 4E+35 meters.

My advice is to have the land/sea mask of parent and child grid be exactly the same in the few grid points adjacent to the child perimeter.
John Wilkin: DMCS Rutgers University
71 Dudley Rd, New Brunswick, NJ 08901-8521, USA. ph: 609-630-0559 jwilkin@rutgers.edu

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arango
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Re: blowing up on nested grid

#4 Post by arango » Mon Aug 13, 2018 6:08 pm

That can be also a problem. However, the main issue here is that there are one or more grid cells with a value of 1E+40 1/km for both inverse metric factors pm and pn. We cannot multiply those variables with the mask because of division by zero in ROMS. The grid spacing (DX=1/pm and DY=1/pn) is a fundamental physical quantity of the grid. The value 1E+40 and its inverse is quite peculiar and we don't use that special value in ROMS or contact point scripts. Something went wrong in the grid generation. We don't have any information if it is a refined grid or not.

jitraporn13
Posts: 11
Joined: Mon May 02, 2016 12:54 pm
Location: Kasetsart University

Re: blowing up on nested grid

#5 Post by jitraporn13 » Wed Aug 22, 2018 8:12 am

Dear All

Thank you so much for your replying. After your suggestion, I rechecked all grid files and contact file.
The problem was from my contact file.
So, I fixed it already.

Thank you so much,
Jitraporn

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