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Use of nu in simpleFoam

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Old   June 23, 2017, 07:57
Question Use of nu in simpleFoam
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nicky chaigneau
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Hello everyone, I am new to cfd especially to openfoam. I try to implement a solver Tsimplefoam wich is simplefoam with temperature fields.

When I discover the file simpleFoam.C I see that the transportProperties was not called. Does it mean that simpleFoam doesn't use nu ? I find it very strange because Navier-Stoke steady-state still have the viscosity parameter.
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Old   June 23, 2017, 17:08
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Lasse Brams Vinther
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Hello Nicky,
Well the simpleFoam solver does include the nu property from the transportProperties, however, not everything of the solver is defined in the simpleFoam.C folder or createFields. If you consider the options file in the make folder, -I$(LIB_SRC)/transportModels/incompressible/singlePhaseTransportModel \ is included and if you look at the singlePhaseTransportModel.H the following piece of code secures the loading of the nu viscosity:

Code:
    IOdictionary
    (
        IOobject
        (
            "transportProperties",
            U.time().constant(),
            U.db(),
            IOobject::MUST_READ_IF_MODIFIED,
            IOobject::NO_WRITE
        )
    ),
    viscosityModelPtr_(viscosityModel::New("nu", *this, U, phi))
which is quite similar to the code in the createFields dictionary.

If you want a varying nu model as a function of the temperature you could implement it yourself.

I have attached a TemperatureSimpleFoam solver and a viscosity model, which varies with temperature depending on the specified coefficients.

Hope its of any use and let me know if you have any questions.
Attached Files
File Type: gz TemperatureSimpleFoamAndNuTemperature.gz (3.7 KB, 36 views)
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Old   June 24, 2017, 01:46
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Thank you very much for your reply. I understand better how it works. Implementing nu as a function of temperature is a great idea to train my self with openFOAM. I will try to do it with your file as a model.

Thank you it is great
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Old   September 8, 2018, 20:53
Default using nu nu[...]
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Federico Agustín Caccia
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I have found different results in simulations using in transportProperties:


HTML Code:
nu              [0 2 -1 0 0 0 0] 4.43e-5


and


HTML Code:
nu              nu[0 2 -1 0 0 0 0] 4.43e-5

why could be that?
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Old   September 12, 2018, 05:17
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Lasse Brams Vinther
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Could you perhaps elaborate upon this or attach your case and describe how you have tested this?

Its hard to determine what the reason for this may be without additional information.

Regards Lasse
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Old   September 12, 2018, 09:31
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Quote:
Originally Posted by Swagga5aur View Post
Could you perhaps elaborate upon this or attach your case and describe how you have tested this?

Its hard to determine what the reason for this may be without additional information.

Regards Lasse

Sorry, I found that the error was to write nu glued to the bracket, this way:
nu nu[...]
It seems openfoam couldn''t read that and so apply a default value.
Thanks!
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Old   September 12, 2018, 10:16
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Ah good didn't even notice

Glad that it works now!
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