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Temperature instability in transonic simulation

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Old   March 27, 2021, 08:43
Default Temperature instability in transonic simulation
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Michelangelo
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Hi Fomers,
I have a problem with a transonic simulation. Iím using rhoPimpleFoam (with "transonic yes") and Iím 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?

Attached Images
File Type: png Temperature_Instability.png (63.8 KB, 12 views)
File Type: png Zoom_T_instability.png (107.5 KB, 12 views)
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Old   March 29, 2021, 04:11
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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.
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Old   March 29, 2021, 07:21
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Hi shock77,


Code:
 

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


Code:
 

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.
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Old   March 29, 2021, 07:57
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First, I think you should try that and see if it helps:


Code:
gradSchemes {     default         cellLimited Gauss linear 1; }
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Old   March 29, 2021, 16:26
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Thanks,

now I try as you advised me.

Updates soon.
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Old   April 1, 2021, 16:10
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I tried with cellLimited but the problem is still there.



I'll try other setups.


Thanks anyway for the advice.
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Old   April 1, 2021, 16:21
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You should try to run your simulation first order first. Than step by step increase the order.
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