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deltaT is getting very small on using interFoam solver

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Old   January 14, 2017, 12:17
Default deltaT is getting very small on using interFoam solver
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Dhinesh_Bala
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Dear Foamers,

I am simulating a simple 3D geometry using interFoam. While running interFoam, deltaT is going upto 1e-7 but my actual deltaT is 0.01 and simulation runs for some days : ( Could anyone help me to fix this issue.? I have attached here the snap shot of mesh, U, p_rgh, alpha.water files:

alpha.water:
/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.3.1 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class volScalarField;
object alpha.water;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions [0 0 0 0 0 0 0];

internalField uniform 0;

boundaryField
{

INLET
{
type inletOutlet;
inletValue uniform 1;
value uniform 1;
}

OUTLET
{
type inletOutlet;
inletValue uniform 0;
value uniform 0;
}

FACES
{
type inletOutlet;
inletValue uniform 0;
value uniform 0;

}

OBSTACLES
{
type zeroGradient;
}



defaultFaces
{
type empty;
}
}

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

U:
/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.3.1 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class volVectorField;
location "0";
object U;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField uniform (0 0 0);

boundaryField
{
INLET
{
type fixedValue;
value uniform (0 -0.01 0);
}

OUTLET
{
type zeroGradient;

}

FACES
{
type zeroGradient;
}

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


}


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

p_rgh:
/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.3.1 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class volScalarField;
object p_rgh;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField uniform 0;

boundaryField
{

INLET
{
type zeroGradient;
}

OUTLET
{
type fixedValue;
value uniform 0;
}

FACES
{
type fixedValue;
value uniform 0;

}

OBSTACLES
{
type fixedFluxPressure;
value uniform 0;
}

}

// ************************************************** *********************** //
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File Type: png snap.png (37.9 KB, 93 views)
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Old   January 14, 2017, 23:45
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Pete Bachant
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Try turning off the automatic time step adjustment in the controlDict first. This may cause your simulation to crash however. Are you running setFields before interFoam to get the initial alpha distribution setup?
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Old   January 15, 2017, 05:57
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Thanks for the reply pbachant.. I have tried turning off "adjustable run time" but my courent no became too large and simulation stopped with core dumped error (pls refer screen shot).. is there any other option to try it out?

I am not using setFields Instead I have mentioned water fields in the alpha.water file


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File Type: png Screenshot from 2017-01-15 12:44:12.png (173.8 KB, 127 views)

Last edited by dhineshcecfd; January 15, 2017 at 07:50.
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Old   January 15, 2017, 08:54
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Hi All,

I found the solution of the above problem. The problem was with deltaT in controlDict and it was very large when compared to my smallest element in the grid.

Thanks for your answer.
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Old   January 15, 2017, 12:11
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What are you trying to simulate? It looks like the way you have it setup, you'll have an infinitesimally thin layer of water at the inlet, and that's it.
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Old   January 15, 2017, 13:07
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I am just trying to find the permeability of this geometry.. so the water is continuously flowing from inlet to outlet..I will measure pressure drop once the flow reaches steady state

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Old   August 6, 2018, 16:29
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Charles
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Quote:
Originally Posted by dhineshcecfd View Post
Hi All,

I found the solution of the above problem. The problem was with deltaT in controlDict and it was very large when compared to my smallest element in the grid.

Thanks for your answer.
Hello,
I am also facing the same problem. Does the smallest element mean the minimum face area or the minimum volume? Was the solution to your problem was to make the magnitude of delta T equal to minimum face area or the minimum volume?
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Old   August 18, 2018, 19:11
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Am also looking at a similar problem, could you explain a little bit please!!!
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Old   August 19, 2018, 13:27
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Quote:
Originally Posted by charlescfd View Post
Hello,
I am also facing the same problem. Does the smallest element mean the minimum face area or the minimum volume? Was the solution to your problem was to make the magnitude of delta T equal to minimum face area or the minimum volume?
Hi,
Minimum deltaT (time_step) is based on your smallest size of grid in you mesh..if you know your minimum size of your cell you can approximately predict the deltaT based on courant no
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Old   August 9, 2022, 08:53
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Quote:
Originally Posted by vivek05 View Post
Hi,
Minimum deltaT (time_step) is based on your smallest size of grid in you mesh..if you know your minimum size of your cell you can approximately predict the deltaT based on courant no
do you leave alone the U magnitude?
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Old   September 4, 2022, 03:33
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Quote:
Originally Posted by vivek05 View Post
Hi,
Minimum deltaT (time_step) is based on your smallest size of grid in you mesh..if you know your minimum size of your cell you can approximately predict the deltaT based on courant no
May you explain to me in details. I face the same problem. I run in olaFlow solver with solitary wave propagation. the smallest mesh size: 0.1 m in Z direction, Delta T = 0.1 s. Co= 0.5.
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