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-   -   non uniform nu model (https://www.cfd-online.com/Forums/openfoam-solving/109031-non-uniform-nu-model.html)

batta31 November 7, 2012 11:19
non uniform nu model
 
Hi guys, I've got a question:
I would like to set up a simulation with a "laminar" turbulence model, but with non uniform values of nu over the domain. Is that possible in openFoam?

Thanks
Simone

kmooney November 8, 2012 09:52
Do you mean that you want a non-uniform Newtonian viscosity field?

batta31 November 8, 2012 10:53
Yes, actually I want to use the distribution of nut of a different simulation and apply it to my new case, which has to run as a laminar case but with non uniform viscosity. :)

kmooney November 8, 2012 11:18
Quote:
Originally Posted by batta31 (Post 391047)
Yes, actually I want to use the distribution of nut of a different simulation and apply it to my new case, which has to run as a laminar case but with non uniform viscosity. :)
If you can create a volScalarField out of your old nut distrubution perhaps like this:

Code:
volScalarField myNuField = nut;
You should be able to drop it into the diffusion term in most any solver as such:

Code:
        fvVectorMatrix UEqn
        (
            fvm::ddt(U)
          + fvm::div(phi, U)
          - fvm::laplacian(myNuField, U)
        );
Cheers!

batta31 November 8, 2012 11:30
That's a very clever idea! Thank you very much kmooney, I'll try as soon as I can. If it doesn't work I'll come back.

Cheers!

batta31 January 31, 2013 09:27
Hi again,
I come back to this thread because I've a doubt..

Since I have a non-uniform field of viscosity, besides the term suggested,

fvm::laplacian(myNuField, U)

shouldn't I insert even a term like:

(fvc::grad(U) & fvc::grad(myNuField)


To better understand my reasoning, think you have to derive the NS equation but with non-uniform spatial viscosity..if you then explode the viscous term,

div(nu*grad(U))

you should obtain both the terms above, right?

Cheers
Simone


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