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interFoam rotating cylinder pressure BC problem

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Old   August 8, 2013, 03:05
Question interFoam rotating cylinder pressure BC problem
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Christian Butcher
Join Date: Jul 2013
Location: Japan
Posts: 84
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Hi,

I'm currently using interFoam to model a rotating cylinder containing mostly water, with air in a small fraction at the top. I initially tried using swak4Foam to create expressions for 0/U on the walls and base of my cylinder making them, for example, (-Rsin(theta), Rcos(theta), 0) for the walls, and similar for the bottom. I have since moved to rotatingWallVelocity in the hope that the wall term would change my problem, but it seems to have made no difference.

When I visualise the results (currently I only have results for a short simulated time, t around 1 second in etc, although am running a 20s duration calculation on a coarser mesh to try track this down), the velocity is set nicely on the boundaries, but then does not diffuse inwards. Instead, the vortex formed in the centre on the axis diffuses velocity outwards.

If anyone has any recommendations (preferably avoiding redesigning my mesh, but if that is necessary then so be it), I would very much appreciate your help.

My BC files are below

p.s.
Looking at my BC files again, I realise it may appear as though there is a hole in my bucket... This is not the case, although the mesh was designed to allow me to set one up, probably using a pressureOutlet condition, or something. As it stands, the outlet should (I hope) behave in exactly the same way as the bottom boundary/patch.

************************************************** *********

Code:
 object      p_rgh;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField   uniform 0;

boundaryField
{
    sides
    {
        type            fixedGradient;
    gradient        uniform 0;
    }

    bottom
    {
        type            fixedGradient;
        gradient        uniform 0;
    }

    outlet
    {
        type            fixedGradient;
        gradient        uniform 0;
    }

    top
    {
        type            totalPressure;
        p0              uniform 0;
        U               U;
        phi             phi;
        rho             rho;
        psi             none;
        gamma           1;
        value           uniform 0;
    }
}
Code:
  object      U;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField   uniform (0 0 0);

boundaryField
{
    sides
    {
    type    movingWallVelocity;
    axis    (0 0 1);
    origin     (0 0 0);
    omega    1;
    value    uniform (0 0 0);
    }
    
   bottom   
    {
    type    movingWallVelocity;
    axis    (0 0 1);
    origin    (0 0 0);
    omega    1;
    value    uniform (0 0 0);
    }

    outlet
    {
    type    movingWallVelocity;
    axis    (0 0 1);
    origin    (0 0 0);
    omega    1;
    value    uniform (0 0 0);
    }

    top
    {
        type            pressureInletOutletVelocity;
    value        uniform (0 0 0);
    }
    
}
Attached Files
File Type: gz MinWorking.tar.gz (5.4 KB, 4 views)

Last edited by chrisb2244; August 12, 2013 at 01:39. Reason: Added an archive containing 0, constant and system directories.
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Old   August 12, 2013, 01:37
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Christian Butcher
Join Date: Jul 2013
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I now have results for a endTime=60 seconds. The velocity is in fact seeming to diffuse outwards from the centre on the surface, and then downwards through my cylinder. I still don't see why the walls are not causing a velocity to diffuse inwards from the walls.

My surface tension is being ignored using a zeroGradient BC on alpha1 as in the damBreak tutorial - is this a bad choice for my problem?

Any help is much appreciated.
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