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Pressure instability with rhoSimpleFoam

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Old   February 17, 2011, 13:30
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Patty
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Quote:
Originally Posted by aerothermal View Post
One thing that helped a lot was to mirror the mesh.
In case of cylinder I mirrored it at mid plane from top to bottom.
So the numerical disturbances did not cause any further symmetry issues.
I can understand it can help, but real life is not always symmetric...Unfortunately, my actual case is not symmetric, and with a porous area...
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Old   February 17, 2011, 14:04
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Quote:
Originally Posted by alberto View Post
Your fvSolution has a nUCorrectors, while the correct syntax in rhoPorousSimpleFoam is nCorrectors.

Best,
Hi Alberto

Are you sure? I made a research like that on my PC:
grep -r nUCorrectors /opt/openfoam171 | grep rhoPorous
and found always nUcorrectors. Moreover, I found it from haukurtReport Tutorial describing the use of rhoPorousSimpleFoam at this address
http://http://www.tfd.chalmers.se/~hani/kurser/OS_CFD_2008/HaukurElvarHafsteinsson/haukurReport.pdf

Isn't "nCorrectors" for RhoPisoFoam alone?

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Old   February 17, 2011, 15:00
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My bad. It seems nUCorrectors is used in porous solvers. Sorry for the confusion!

nCorrectors is for PISO and PIMPLE, and they have a different role there.
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Old   February 17, 2011, 16:20
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Originally Posted by alberto View Post
You are going to have a sort of wave reflection at the outlet I think. Maybe you want to give a try to waveTransmissive BC's and an unsteady run (rhoPisoFoam, rhoPimpleFoam).
Hi Alberto

I think neither RhoPisoFoam nor rhoPimpleFoam have a concept of porous zone, am I right?

I will try wave transmissive BC's but how to set it is not clear for me. Any suggestion?

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Old   February 17, 2011, 17:08
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Hi, yes they do not have the porous zone implemented, but adding it should be easy, even if it means modifying a solver.

Anyway, my suggestion was mainly to understand what is going on. The BC can be set as shown in the rhoPisoFoam LES tutorial:

Code:
outlet          
    {
        type            waveTransmissive;
        field           p;
        phi             phi;
        rho             rho;
        psi             psi;
        gamma           1.3;
        fieldInf        1e5;
        lInf            0.3;
        value           uniform 1e5;
    }
Best,
Alberto
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