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pimpleFoam(transient) vs simpleFoam(steady)

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Old   February 21, 2022, 18:29
Default pimpleFoam(transient) vs simpleFoam(steady)
  #1
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Farzad Faraji
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Hello all
I am simulating artery(see attached picture), and I only need steady state solution. As you know, we can change transient to steady state inside fvSchemes as below;

Code:
ddtSchemes
{
    default         steadyState; //Euler;
}
but steady state fails and only pimple-transient works fine, why?

Code:
pimple transient ===>works
pimple steady ===>Fails
*************
simple transient ===>Fails
simple steady ===>Fails
Thanks,
Farzad
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File Type: png cfdonline.PNG (97.3 KB, 10 views)
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Old   February 21, 2022, 18:43
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mohammad
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Quote:
Originally Posted by farzadmech View Post
Hello all
I am simulating artery(see attached picture), and I only need steady state solution. As you know, we can change transient to steady state inside fvSchemes as below;

Code:
ddtSchemes
{
    default         steadyState; //Euler;
}
but steady state fails and only pimple-transient works fine, why?

Code:
pimple transient ===>works
pimple steady ===>Fails
*************
simple transient ===>Fails
simple steady ===>Fails
Thanks,
Farzad

Hi Farzad,
We need to see the log output to see what happens for each case. SIMPLE, in OF, does not contain any time derivative:
Code:
tmp<fvVectorMatrix> tUEqn
    (
        fvm::div(phi, U)
      + MRF.DDt(U)
      + turbulence->divDevReff(U)
     ==
        fvOptions(U)
    );

However, PIMPLE, in essence, is the combination of SIMPLE and PISO. Therefore, it is a transient solver:
Code:
tmp<fvVectorMatrix> tUEqn
(
    fvm::ddt(U) + fvm::div(phi, U)
  + MRF.DDt(U)
  + turbulence->divDevReff(U)
 ==
    fvOptions(U)
);
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Old   February 21, 2022, 19:18
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  #3
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Farzad Faraji
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Dear Mohammad
Please see the logs which I attached here. I think I should increase nCorrectors.

Code:
SIMPLE //PIMPLE
{
    nOuterCorrectors 1;
    nCorrectors     2;
    nNonOrthogonalCorrectors 0;
    pRefCell        0;
    pRefValue       0;
}
Thanks,
Farzad
Attached Images
File Type: jpg pimpleState.jpg (94.4 KB, 14 views)
File Type: jpg simpleSteadyState.jpg (84.5 KB, 12 views)
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Old   February 21, 2022, 22:23
Default My problem is solved
  #4
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Farzad Faraji
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Dear Mohammad
My problem is solved. I just used simpleFoam files(controlDict, fvSchemes fvSolution) in;
Code:
/openfoam9/tutorials/incompressible/simpleFoam/pitzDaily/system
and it works fine. Just a question, I want to plot residuals and when I use log scale, it works fine which I have attached. On the other hand, when I use normal scale, it does not plot anything. why?
Attached Images
File Type: jpg photo_2022-02-22_03-22-31.jpg (32.5 KB, 20 views)
File Type: png Plot.png (128.1 KB, 16 views)
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openfoam, pimplefoam, simplefoam, steady state, transient

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