[MIZOR]

Hi Fomers,
I have a problem with a transonic simulation. I’m using rhoPimpleFoam (with "transonic yes") and I’m progressively reaching the outlet target solution. However when the solution is close to the sonic condition, an instability of temperature field appears as shown in the attached images.


Has anyone already found this instability?

[shock77]

Can you share your fvSchemes and controldict?


I suppose you are using high order schemes with a big timestep, thats why those oscillations might occure.

[MIZOR]

Hi shock77,

 

FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      fvSchemes;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

ddtSchemes
{
    default         Euler;
}

gradSchemes
{
    default         Gauss linear;
    grad(U)         cellLimited Gauss linear 1;
}

divSchemes
{
    default         none;

    div(phi,U)      Gauss limitedLinearV 1;

    turbulence      Gauss upwind;
    energy          Gauss limitedLinear 1;

    div(phi,k)      $turbulence;
    div(phi,omega)  $turbulence;

    div(phi,e)      $energy;
    div(phi,h)      $energy;
    div(phi,K)      $energy;
    div(phi,Ekp)    $energy;

    div(phid,p)     Gauss limitedLinear 1;
    div(phiv,p)     Gauss limitedLinear 1;
    div((phi|interpolate(rho)),p)  Gauss linear;

    div(((rho*nuEff)*dev2(T(grad(U)))))    Gauss linear;
}laplacianSchemes
{
    default         Gauss linear corrected;
}

interpolationSchemes
{
    default         linear;
}

snGradSchemes
{
    default         corrected;
}

wallDist
{
    method meshWave;
}

and

 

FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    location    "system";
    object      controlDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

application     rhoPimpleFoam;

startFrom       latestTime;

startTime       0;

stopAt          endTime;

endTime         0.5;

deltaT          1e-5;

writeControl    adjustable;

writeInterval   0.001;

purgeWrite      0;

writeFormat     ascii;

writePrecision  10;

writeCompression off;

timeFormat      general;

timePrecision   9;

runTimeModifiable true;

adjustTimeStep  yes;

maxCo           1;

maxDeltaT       1e-3;

minDeltaT       1e-6;

Yesterday I tested Gauss limitedVanLeer -2.0 3.0; for $energy and it improved the instability but it crashed anyway near the sonic condition.

[shock77]

First, I think you should try that and see if it helps:

gradSchemes {     default         cellLimited Gauss linear 1; }

[MIZOR]

Thanks,

now I try as you advised me.

Updates soon.

[MIZOR]

I tried with cellLimited but the problem is still there.



I'll try other setups.


Thanks anyway for the advice.

[shock77]

You should try to run your simulation first order first. Than step by step increase the order.