[stamufa]

Hey Foamers,


I was testing out the rhoPimpleFoam solver and I made a simple wind tunnel box. I'm curious why the solution diverges, and the residuals oscillate wildly.



The problem is severe for lower velocities. The oscillation stops when I set the initial U to 1, but the pressure residual is very high. I can reason with that because compressible solvers probably don't do so well at lower Ma values (well, what I do know for sure is that they are slower, I'm not sure if they are unstable too).



Velocity

Uinlet          (100 0 0);

dimensions      [0 1 -1 0 0 0 0];

internalField   uniform (0 0 0);

boundaryField
{
    left
    {
        type            fixedValue;
        value           uniform $Uinlet;
    }

    right
    {
        type            inletOutlet;
        inletValue      uniform (0 0 0);
        value           uniform (10 0 0);
    }

    bottom
    {
        type            fixedValue;
        value           uniform (0 0 0);
    }

    top
    {
        type            fixedValue;
        value           uniform (0 0 0);
    }

   back
    {
        type            symmetryPlane;
    }

   front
    {
        type            symmetryPlane;
    }

    #includeEtc "caseDicts/setConstraintTypes"
}

Pressure

dimensions      [1 -1 -2 0 0 0 0];

internalField   uniform 1e5;

boundaryField
{

  left
    {
        type            zeroGradient;
    }

    right
    {  type            fixedValue;
        value           $internalField;
       
    }

    bottom
    {
        type            zeroGradient;
    }

    top
    {
        type            zeroGradient;
    }

   back
    {
        type            symmetryPlane;
    }

   front
    {
        type            symmetryPlane;
    }

    #includeEtc "caseDicts/setConstraintTypes"
}

Are there any errors that are obvious?

[HenrikJohansson]

Hi Mustafa,

For your velocity outlet you could try the pressureInletOutletVelocity B.C.
Why have you set the inital value of your outlet to (10 0 0)? Should it not be (0 0 0)?

What schemes are you using?