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Old   September 1, 2010, 06:25
Default not outflow at outlet in interFoam
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Nico T
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Hi,
I've a simple square geometry with a irregular (up-and down) bottom. BC are inlet, outlet, top-atmosphere and walls in interFoam laminar. The model runs but not with my expected results. The problem is, that there's no outflow at the outlet. Looks like a closed wall, liquid (aplha1) is bouncing backwards.
checkMesh is OK.
My BC:

p_rgh:

inlet
{ type zeroGradient; } outlet { type fixedValue; value uniform 0; }

U:

inlet
{ type fixedValue; value uniform (0.5 0 0); } outlet { type zeroGradient; }

alpha1:

inlet { type fixedValue; value uniform 1; } outlet { type inletOutlet; inletValue uniform 0; value uniform 0; }
Thanks for help,

Nico
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Old   September 2, 2010, 02:50
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Quote:
Originally Posted by deniggo View Post
alpha1:

inlet { type fixedValue; value uniform 1; } outlet { type inletOutlet; inletValue uniform 0; value uniform 0; }
I think you force alpha1 to be zero at the outlet with this condition.
I would suggest you use zeroGradient for the outlet of alpha1.
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Old   September 2, 2010, 03:02
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Thanks for your answer,
setting alpha1 on zeroGradient was my step before. The model runs only 1-2 seconds and this error message occurs:

MULES: Solving for alpha1
#0 Foam::error:rintStack(Foam::Ostream&) in "/home/trauth/OpenFOAM/OpenFOAM-1.7.0/lib/linux64GccDPOpt/libOpenFOAM.so" #1 Foam::sigFpe::sigFpeHandler(int) in "/home/trauth/OpenFOAM/OpenFOAM-1.7.0/lib/linux64GccDPOpt/libOpenFOAM.so" #2 in "/lib64/libc.so.6"
#3 void Foam::MULES::limiter<Foam::geometricOneField, Foam::zeroField, Foam::zeroField>(Foam::Field<double>&, Foam::geometricOneField const&, Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> const&, Foam::GeometricField<double, Foam::fvsPatchField, Foam::surfaceMesh> const&, Foam::GeometricField<double, Foam::fvsPatchField, Foam::surfaceMesh> const&, Foam::zeroField const&, Foam::zeroField const&, double, double, int) in "/home/trauth/OpenFOAM/OpenFOAM-1.7.0/lib/linux64GccDPOpt/libfiniteVolume.so"
#4 void Foam::MULES::explicitSolve<Foam::geometricOneField , Foam::zeroField, Foam::zeroField>(Foam::geometricOneField const&, Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh>&, Foam::GeometricField<double, Foam::fvsPatchField, Foam::surfaceMesh> const&, Foam::GeometricField<double, Foam::fvsPatchField, Foam::surfaceMesh>&, Foam::zeroField const&, Foam::zeroField const&, double, double) in "/home/trauth/OpenFOAM/OpenFOAM-1.7.0/lib/linux64GccDPOpt/libfiniteVolume.so"
#5 Foam::MULES::explicitSolve(Foam::GeometricField<do uble, Foam::fvPatchField, Foam::volMesh>&, Foam::GeometricField<double, Foam::fvsPatchField, Foam::surfaceMesh> const&, Foam::GeometricField<double, Foam::fvsPatchField, Foam::surfaceMesh>&, double, double) in "/home/trauth/OpenFOAM/OpenFOAM-1.7.0/lib/linux64GccDPOpt/libfiniteVolume.so"
#6 in "/home/trauth/OpenFOAM/OpenFOAM-1.7.0/applications/bin/linux64GccDPOpt/interFoam"
#7 __libc_start_main in "/lib64/libc.so.6"
#8 at /usr/src/packages/BUILD/glibc-2.11.2/csu/../sysdeps/x86_64/elf/start.S:116
Gleitkomma-Ausnahme



Any idea what could be the reason?

Thanks
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Old   September 2, 2010, 11:23
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Hm, this is strange indeed.
It concerns the MULES solver for solving the VOF-equation.

I would suggest you to re-check everything converning alpha1 including boundaries and initial condition.
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Old   September 2, 2010, 22:53
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Can you post a little pic about the geometry?

Bye.
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Old   September 3, 2010, 03:54
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Here's my geometry.
- Inlet on the left, outlet on the right side, both bc are only in the lower part of the sidewalls.
- The top boundary is set as atmosphere.
- Bottom, front, and backside are walls.

The Mesh is coarse, maybe refinement would lead to better results?!
Thanks for your help.

Nico

[IMG]file:///home/trauth/Dokumente/Graphics/geo.jpg[/IMG]
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File Type: jpg geo.jpg (58.8 KB, 122 views)
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Old   September 3, 2010, 04:08
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Quote:
Originally Posted by deniggo View Post
Here's my geometry.
- Inlet on the left, outlet on the right side, both bc are only in the lower part of the sidewalls.
How do you tell OpenFOAM to do that?

Quote:
Originally Posted by deniggo View Post
The Mesh is coarse, maybe refinement would lead to better results?!
A hexahedronal mesh can lead to better results.

How does your initialisation of alpha1 look like?
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Old   September 3, 2010, 04:33
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Quote:
Originally Posted by sega View Post
How do you tell OpenFOAM to do that?
I've defined boundaries in blender and engrid before.

0/alpha1, in this case OF crashes after 1.78 sec.

right and left are the sidewalls above inlet and outlet.

Code:
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    location    "0";
    object      alpha1;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions      [0 0 0 0 0 0 0];

internalField   uniform 0;

boundaryField
{
    right
    {
        type            zeroGradient;
    }
    inlet
    {
        type            fixedValue;
        value           uniform 1;
    }
    outlet
    {
        type            zeroGradient;
    }
    front
    {
        type            zeroGradient;
    }
    back
    {
        type            zeroGradient;
    }
    top
    {
        type            inletOutlet;
        inletValue      uniform 0;
        value           uniform 0;
    }
    bottom
    {
        type            zeroGradient;
    }
    left
    {
        type            zeroGradient;
    }
}
0/alpha1 in this case OF runs, but outlet is closed. outlet is set to inletOutlet
Code:
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    location    "0";
    object      alpha1;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions      [0 0 0 0 0 0 0];

internalField   uniform 0;

boundaryField
{
    right
    {
        type            zeroGradient;
    }
    inlet
    {
        type            fixedValue;
        value           uniform 1;
    }
    outlet
    {
        type            inletOutlet;
        inletValue      uniform 0;
        value           uniform 0;
    }
    front
    {
        type            zeroGradient;
    }
    back
    {
        type            zeroGradient;
    }
    top
    {
        type            inletOutlet;
        inletValue      uniform 0;
        value           uniform 0;
    }
    bottom
    {
        type            zeroGradient;
    }
    left
    {
        type            zeroGradient;
    }
}
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Old   September 3, 2010, 08:14
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Hello Nico, first settings appear to be correct, except for:

Quote:
top
{
type inletOutlet;
inletValue uniform 0;
value uniform 0;
}
I think is better to user zeroGradient too over there. I would use inletOutlet for U in atmo. Can you post your U and p dicts for /0 and the initialization?

A little shortcut to start with this problem is to put a wall on the top (atmosphere) and to use inletOutlet in the top part of the inlet to ensure air entrance.

Regards.
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Old   September 3, 2010, 09:26
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Hello Santiago,

Here my 0/U:
I guess pressureInletOutletVelocity equates almost to inletOutlet.
Code:
FoamFile
{
    version     2.0;
    format      binary;
    class       volVectorField;
    location    "0";
    object      U;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField   uniform (0 0 0);

boundaryField
{
    right
    {
        type  fixedValue;
        value uniform (0 0 0);
    }
    inlet
    {
        type  fixedValue;
        value uniform (0.5 0 0);
    }
    outlet
    {
        type zeroGradient;
    }
    front
    {
        type  fixedValue;
        value uniform (0 0 0);
    }
    back
    {
        type  fixedValue;
        value uniform (0 0 0);
    }
    top
    {
        type inletOutlet; 
            inletValue uniform (0 0 0); 
            value uniform (0 0 0); 

        //before:
        //type   pressureInletOutletVelocity;
        //value  uniform (0 0 0);
    }
    bottom
    {
        type  fixedValue;
        value uniform (0 0 0);
    }
    left
    {
        type  fixedValue;
        value uniform (0 0 0);
    }
}
and 0/p_rgh:

Code:
FoamFile
{
    version     2.0;
    format      binary;
    class       volScalarField;
    object      p_rgh;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField   uniform 0;

boundaryField
{
    right
    {
        type            buoyantPressure;
        value           uniform 0;
    }
    inlet
    {
        type            zeroGradient;
    }
    outlet
    {
        type            fixedValue;
        value           uniform 0;
    }
    front
    {
        type            buoyantPressure;
        value           uniform 0;
    }
    back
    {
        type            buoyantPressure;
        value           uniform 0;        
    }
    top
    {
        type            totalPressure;
        p0              uniform 0;
        U               U;
        phi             phi;
        rho             rho;
        psi             none;
        gamma           1;
        value           uniform 0;
    }
    bottom
    {
        type            buoyantPressure;
        value           uniform 0;
    }
    left
    {
        type            buoyantPressure;
        value           uniform 0;
    }
    
}
In another run, I changed all buoyantPressure into zeroGradient with no effect.


Do you mean the boundaray-file with initialization?:

Code:
FoamFile
{
    version     2.0;
    format      ascii;
    class       polyBoundaryMesh;
    location    "constant/polyMesh";
    object      boundary;
}

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

8
(
    right
    {
        type        wall;
        nFaces      29;
        startFace   11746;
    }
    inlet
    {
        type        patch;
        nFaces      26;
        startFace   11775;
    }
    outlet
    {
        type        patch;
        nFaces      26;
        startFace   11801;
    }
    front
    {
        type        wall;
        nFaces      879;
        startFace   11827;
    }
    back
    {
        type        wall;
        nFaces      907;
        startFace   12706;
    }
    top
    {
        type        patch;
        nFaces      482;
        startFace   13613;
    }
    bottom
    {
        type        wall;
        nFaces      478;
        startFace   14095;
    }
    left
    {
        type        wall;
        nFaces      33;
        startFace   14573;
    }
)
Quote:
I think is better to user zeroGradient too over there. I would use inletOutlet for U in atmo.
OK, I replaced:

aplha1: inletOutlet into zeroGradient

U: pressureInletOutletVelocity
into
type inletOutlet;
inletValue uniform (0 0 0);
value uniform (0 0 0);

interFoam runs only 1.3 seconds.

Quote:
A little shortcut to start with this problem is to put a wall on the top (atmosphere) and to use inletOutlet in the top part of the inlet to ensure air entrance.
I'll try this next.

Thanks for help.

Regards,

Nico
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Old   September 3, 2010, 12:48
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Nico, your settings appear to be OK, I only would change (as you already did) the bouyantPressure BC by zeroGradient. Pressure equation is Poisson-like, therefore zeroGradient is the correct BC for walls. I would use these settings with a very small timestep, i.e. 1e-7, and then would increase it until run explodes.

Try this, if you continue having problems, please post the output.

Good luck.
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Old   September 7, 2010, 11:17
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Hi,

I forgot to give aplha1 in setFields a value, I neglected it before (thanks to Sega). My geometry is now half filled with water at time 0. InterFoam runs.

Quote:
I only would change (as you already did) the bouyantPressure BC by zeroGradient.
I replayced boyantPressure by zeroGradient and no changes occurred. Maybe in my case, it makes no differences?
I took the BC from the damBreak tutorial. I think at least here, correct BC should be used.

Thanks,

Nico
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Old   May 11, 2012, 04:24
Default no outflow in interFoam
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dear FOAMERS,

I used type inletOutlet; inletValue uniform (0 0 0); for U at the outlet and type zeroGradient; for alpha1 at the outlet and tried aswell type inletOutlet; inletValue uniform 0; for alpha1, and all these settings work fine with OF 1.7.1 but create no outflow at OF 2.1.x., so maybe there is some change between the versions?
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Old   May 11, 2012, 06:07
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using PISO instead of PIMPLE solved the problem
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Old   May 23, 2012, 06:22
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Ok turning old searching the cause of alpha1 being reflected at the outflow, I finally got it (ints not about PISO and PIMPLE). Maybe this is a bug dependent on ubuntu version, but it is quite relevant. The difference between the two pictures below showing an outflow of a channel is only that I moved the grid from positive x quadrant to negative x quadrant. When the whole grid lies at a position that the x-coordinates are smaller than 0 the outflow works! If using zeroGradient for p_rgh at the outflow, it works aswell fine for a grid with positive x coordinates. Anyway, I would be happy for any explanation on this.
Attached Images
File Type: jpg impactOnOutflowT0,15.jpg (13.2 KB, 307 views)
File Type: jpg impactOnOutflowT0,15_withXCoordsmallerZero.jpg (14.6 KB, 22 views)

Last edited by vonboett; June 14, 2012 at 09:06.
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