pimpleFoam(transient) vs simpleFoam(steady)

farzadmech · February 21, 2022, 18:29

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

mostanad · February 21, 2022, 18:43

Quote:

Originally Posted by farzadmech

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)
);

farzadmech · February 21, 2022, 19:18

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

farzadmech · February 21, 2022, 22:23

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?