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Old   August 20, 2019, 02:30
Default LES diesel jet
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Brett
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Hi guys,

I'm trying to simulate a diesel jet using LES.
I'm trying to run compressibleMultiInterFoam.

I think I'm getting close but I keep getting this error:

Creating field kinetic energy K

Courant Number mean: 0.0020326 max: 2487.28


--> FOAM FATAL ERROR:
Different dimensions for =
dimensions : [0 2 -1 0 0 0 0] = [1 -1 -1 0 0 0 0]


From function bool Foam::dimensionSet:perator=(const Foam::dimensionSet&) const
in file dimensionSet/dimensionSet.C at line 171.

FOAM aborting


Any thoughts???
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Old   August 20, 2019, 05:04
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Wrong unit change it the way the solver already told you
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Old   August 20, 2019, 05:07
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Thanks.

What file do I need to change though??
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Old   August 20, 2019, 09:29
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It looks like the "nut" file
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Old   August 20, 2019, 19:56
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Thanks for that.

So it's wanting me to change the units of the nut file essentially.
I wasn't aware the units of that had to change from incompressible to compressible flow?
How did you figure out it was nut that needed changing? very interesting...
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Old   August 20, 2019, 21:05
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Interestingly...

After changing the units of the nut file the error reoccurs:

Creating field kinetic energy K

Courant Number mean: 0.00020326 max: 248.728


--> FOAM FATAL ERROR:
Different dimensions for =
dimensions : [1 -1 -1 0 0 0 0] = [0 2 -1 0 0 0 0]


From function bool Foam::dimensionSet:perator=(const Foam::dimensionSet&) const
in file dimensionSet/dimensionSet.C at line 171.

FOAM aborting
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Old   August 21, 2019, 04:31
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Just because of the units, but I was wrong. You have to change the pressure units when you change from incompressible to compressible to you have to check these.
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Old   August 21, 2019, 20:28
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Yeah I already changed them.
Just to be certain what units for 'p' and 'p_rgh' would you be using?
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Old   August 22, 2019, 04:16
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p and p_rgh share the same units:


[1 -1 -2 0 0 0 0];
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Old   August 22, 2019, 20:36
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yep. thats what i've got them set as. hmmm.... seems like ive missed something else then.
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Old   August 26, 2019, 04:19
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You should look at a tutorial and then compare all the units to yours. Including the thermophysical Properties.
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Old   August 26, 2019, 23:36
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Made a breakthrough of sorts.
Looks like it's "alphat" that needed it's units changed.
It runs now. Whether the values I've chosen are physical or not we'll have to see but I've gotten over that issue.
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Old   August 27, 2019, 04:30
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If you do RANS you should use a wallfunction for alphat with a turbulent Prandlt of 0.85, but if you do a LES with a fine grid it doesnt really matter in my experience.


Edit:
I just saw that you are doing LES, so forget about the RANS
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