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stamufa May 16, 2019 05:26
RhoPimpleFOAM: Wind Tunnel Results Oscillate
 
1 Attachment(s)
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



Code:

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

Code:
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 May 22, 2019 03:14
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?


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