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Simulating turbulent flow in rectangle pipe with rhoPimpleFoam

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Old   January 3, 2014, 20:23
Default Simulating turbulent flow in rectangle pipe with rhoPimpleFoam
  #1
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赵庆良
Join Date: Aug 2013
Posts: 56
Rep Power: 3
zqlhzx is on a distinguished road
Hi foamers,
I want to use rhoPimpleFoam to simulate turbulent flow in rectangle piple.here is my mesh,it is simple.
mesh.jpg
The length is 200mm,width and high is 25mm.The detail is in blockMeshdict.
Code:
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      blockMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

convertToMeters 1;

vertices
(
    (0 0 0)
    (0.2 0 0)
    (0.2 0.025 0)
    (0 0.025 0)
    (0 0 0.025)
    (0.2 0 0.025)
    (0.2 0.025 0.025)
    (0 0.025 0.025)

);

blocks
(
    hex (0 1 2 3 4 5 6 7) (100 20 20) simpleGrading (1 1 1)

);

edges
(
);

boundary
(
    bottomWall
    {
        type            wall;
        faces           ((0 4 5 1));
    }
    topWall
    {
        type            wall;
        faces           ((7 6 2 3));
    }

    sides1
    {
        type            wall;
        faces           ((7 4 5 6));
    }
    sides2
    {
        type            wall;
        faces           ((3 0 1 2));
    }


    in
    {
        type            patch;
        faces           ((0 4 7 3));
    }
    out
    {
        type            patch;
        faces           ((1 5 6 2));
    }
);

mergePatchPairs
(
);
The U initial condition is that x-direction is 1m/s,y and z direction are 0.As following:
Code:
dimensions      [ 0 1 -1 0 0 0 0 ];

internalField   uniform (0 0 0);

boundaryField
{
    bottomWall
    {
        type            fixedValue;
        value           uniform (0 0 0);
    }
    topWall
    {
        type            fixedValue;
        value           uniform (0 0 0);
    }
    sides1
    {
        type            fixedValue;
        value           uniform (0 0 0);
    }
    sides2
    {
        type            fixedValue;
        value           uniform (0 0 0);
    }

    in
    {
        type            turbulentInlet;
        referenceField  uniform (1 0 0);
        fluctuationScale (0.1 0.1 0.1);
        value           uniform (1 0 0);
    }
    out
    {
        type            inletOutlet;
        inletValue      uniform (0 0 0);
        value           uniform (0 0 0);
    }
}
The deltaT I used in controlDict is 1e-4.Picture "time0" is my U field at time=0.
time0.jpg
Then I run my case,and I write out a result at every 20 deltaT(The first result is time=0.002).Picture "time1" is U field at time=0.002.
time1.jpg
Please take a look at time1 picture carefully.Just after 0.002s,the outlet's velocity is nearly 1m/s,same as initial vilocity I defined firstly.
Actually,it is unphysical.Because 1m/s*0.002s=2mm.And the mesh length is 200mm,it is impossible that after 0.002s,outlet's velocity is nearly 1m/s.
Could some one tell me that where I was wrong?What cause the problem?
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Old   January 6, 2014, 06:24
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  #2
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HECKMANN Frédéric
Join Date: Jul 2010
Posts: 236
Rep Power: 8
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Put your full case here, it will be easier to check
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