error:different horizontal mixing scheme

[XMUZSM]

Dear ROMS user,
As a beginner I meet some problem that: firstly I defined smagorinsky option and I want to define VISC4' and TNU4' s value, so I caculate these parameter with the (ΔX./pi).^4./dt.
The model is always blow-up in Max speed and Max rho, no matter how I change the value of VISC4 and TNU4.
The following is what happen in my case:

TIME-STEP YYYY-MM-DD hh:mm:ss.ss KINETIC_ENRG POTEN_ENRG TOTAL_ENRG NET_VOLUME
C => (i,j,k) Cu Cv Cw Max Speed

0 2013-01-01 00:00:00.00 2.17E-02 -2.12E+04 -2.12E+04 7.02E+16 2.08E+02s
(221,0521,24) 2.85E+00 1.42E+00 0.00E+00 3.19E+00
DEF_AVG - creating average file, Grid 01: /data/gpfs01/ywjiang/zsm/CROCO_FILES/scs_result/VIS4_test_avg_0001.nc
DEF_DIAGS - creating diagnostics file, Grid 01: /data/gpfs01/ywjiang/zsm/CROCO_FILES/scs_result/VIS4_testforenergy_0001.nc
1 2013-01-01 00:01:30.00 2.17E-02 -2.12E+04 -2.12E+04 7.02E+16 1.97E+00s
(222,0522,23) 2.90E+00 1.46E+00 1.68E-03 3.28E+00
2 2013-01-01 00:03:00.00 2.16E-02 -2.12E+04 -2.12E+04 7.02E+16 7.77E-01s
(112,0644,02) 1.26E+02 4.81E+01 1.22E-03 1.82E+02
Max speed blow-up
Max rho blow-up
Max speed blow-up
Max rho blow-up
Max speed blow-up
Max rho blow-up
Found Error: 01 Line: 298 Source: ROMS/Nonlinear/main3d.F
Found Error: 01 Line: 298 Source: ROMS/Drivers/nl_ocean.h

Blowing-up: Saving latest model state into RESTART file

Max speed blow-up
Max rho blow-up
Max speed blow-up

And as a beginner,any reply is very helpful to me.

[kate]

Does it run with TNU2? Is this a new domain? Are you sure you have a small enough timestep?

[XMUZSM]

[XMUZSM]

Does it run with TNU2? Is this a new domain? Are you sure you have a small enough timestep?

Thanks, kate!
But it can run with TNU2; the domain is a curve orthogonal grid made by myself; and my dt=90, I think it is small enough.

[kate]

They have different timestep constraints, depending on dx. You could try a shorter timestep to see if it runs.

[XMUZSM]

They have different timestep constraints, depending on dx. You could try a shorter timestep to see if it runs.

Is it CFL condition? Or the t<(Δx/pi).^4./v4? I am confused because I get visc4' s value through the latter

[kate]

Yes, there's a CFL condition. There's also the timescale of damping on the scales you want to damp (2 dx) and the timescale of damping on scales you don't want to damp. A CFL of 1.0 will be unstable. What are you shooting for?

[XMUZSM]

Yes, there's a CFL condition. There's also the timescale of damping on the scales you want to damp (2 dx) and the timescale of damping on scales you don't want to damp. A CFL of 1.0 will be unstable. What are you shooting for?

But my case can run with the same condition except I use VIS2 and TNU2, so I think my dt may fit CFL condition?
And I found my case can run after I change the horizontal mixing scheme from (Mix_GEO_UV and Mix_GEO_TS) to (Mix_S_UV and Mix_S_TS), but why?

[kate]

No, no, no MIX_S_TS! It's a terrible thing to do with a sigma coordinate. Why wouldn't MIX_GEO work? My biggest problems with it
involve wetting and drying and realistic bathymetry. I don't know what you are trying.

I'm just suggesting trying a shorter timestep so that you can rule out CFL troubles. The fact that it blew up so quickly kind of points to a CFL
trouble.

[XMUZSM]

No, no, no MIX_S_TS! It's a terrible thing to do with a sigma coordinate. Why wouldn't MIX_GEO work? My biggest problems with it
involve wetting and drying and realistic bathymetry. I don't know what you are trying.

I'm just suggesting trying a shorter timestep so that you can rule out CFL troubles. The fact that it blew up so quickly kind of points to a CFL
trouble.

Thank you Kate! It almost solved! But I have some question:MIX_GEO is a most reasonable scheme, then why there are the MIX_S? I mean that mixing along constant S-surfaces isn't a real horizontal mixing.

[kate]

It is easy to code up and it makes sense over a flat bottom.