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incompressible multiphase - jet simulation

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Old   September 10, 2015, 10:09
Default incompressible multiphase - jet simulation
  #1
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shashank moghe
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Hello all, I am doing an incompressible, multiphase simulation of a water jet shooting into a cylinder containing stagnant air. I am using interFoam solver. I have refined the grid to have the minimum base cell dimension of 0.2 mm. I am having a really hard time :
1) Getting the solution to stay stable (there are severe spurious velocities in the internal field), whenever I use any 2nd order divergence schemes. I used Gauss linearUpwind grad (U), Gauss vanLeerV 1, Gauss limitedLinearV 1. None of them stop my simulation from blowing up.

2) On a coarser mesh, I can get some simulations to run without blowing up, but the water jet shoots through the domain without showing any signs of break-up. Just a straight beam-like behaviour.

I have come to believe I am doing something wrong with the IC/BCs. Here are my files, I have changed them recently, let me know if they make sense in the context of the problem.



k:
/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.1.1 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class volScalarField;
location "0";
object k;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField uniform 1.5;

boundaryField
{
inflow
{
type turbulentIntensityKineticEnergyInlet;
intensity 0.05;
value uniform 1.5;
//type fixedValue;
//value uniform 1.5; // calculated as per [1.5*pow(U*I,2)], U = mean flow velocity, I = turbulence intensity (assumed 5%)
}
outflow
{
type inletOutlet;
inletValue uniform 1.5;
value uniform 1.5;
//type zeroGradient;
}
wall_imported
{
type kqRWallFunction; // Average y+ = 30
value uniform 1.5;
}
inoutflow
{
type fixedValue;
value uniform 0; // No BL on this patch
}
"proc.*"
{
type processor;
value uniform 0;
}
}


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


nut:

/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.1.1 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class volScalarField;
location "0";
object nut;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField uniform 0; // can be calculated = 1.4e-04, as per [sqrt(3/2)*(U*I*l)], I = turb intensity (assumed 10%), l = turb length scale

boundaryField
{
inflow
{
type calculated;
value uniform 0;
}
outflow
{
type calculated;
value uniform 0;
}
wall_imported
{
type nutkWallFunction; // Average y+ = 30
value uniform 0;
}
inoutflow
{
type fixedValue;
value uniform 0; // No BL on this patch
}
"proc.*"
{
type processor;
value uniform 0;
}
}


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

Omega:

/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.1.1 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class volScalarField;
location "0";
object omega;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField uniform 1e04;

boundaryField
{
inflow
{
type fixedValue;
value uniform 1e04; // clculated as per [sqrt(k)/l], k = turbulence kinetic energy, l = turbulence length scale = (0.038*D) for pipe flows
}
outflow
{
type inletOutlet;
inletValue uniform 1e04;
value uniform 1e04;
//type zeroGradient;
}
wall_imported
{
type omegaWallFunction; // Average y+ = 30
value uniform 1e04;
}
inoutflow
{
type fixedValue;
value uniform 0; // No BL on this patch
}
"proc.*"
{
type processor;
value uniform 0;
}
}


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

p_org:
/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.1.1 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class volScalarField;
location "0";
object p_org;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField uniform 0;

boundaryField
{
inflow
{
type zeroGradient;
}
outflow
{
type fixedValue;
value uniform 0;
}
wall_imported
{
type zeroGradient;
}
inoutflow
{
type zeroGradient;
}
"proc.*"
{
type processor;
value uniform 0;
}
}


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

U:

/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.1.1 |
| \\ / 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
{
inflow
{
type flowRateInletVelocity;
massFlowRate constant 0.1;
value uniform (0 0 0);
//type fixedValue;
//value uniform (-20 0 0);
}
outflow
{
type pressureInletOutletVelocity;
value uniform (0 0 0);
inletValue uniform (0 0 0);
//type zeroGradient;
}
wall_imported
{
type fixedValue;
value uniform (0 0 0);
}
inoutflow
{
type fixedValue;
value uniform (0 0 0);
}
"proc.*"
{
type processor;
value uniform 0;
}
}


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






Sorry for the long post. Any comments will be highly appreciated.
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Old   September 14, 2015, 10:06
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shashank moghe
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No takers?
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Old   October 18, 2015, 19:22
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Francesco Tocci
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Hello Shashank, I am working on a similar case; did you solve the problem?
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Old   October 19, 2015, 10:16
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shashank moghe
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Which one? The stability problem or the jet break up one?
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Old   October 19, 2015, 14:13
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Francesco Tocci
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Actually both. I am using interFoam to simulate the formation of a Taylor bubble in a riser with an initial condition of riser full of (static) liquid.
You are using wall function: how did you calculate y+ for multiphase flow?
Thanks
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Old   October 19, 2015, 14:28
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shashank moghe
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That approach was not working out for me. I should have known better, I was using RANS modeling to simulate secondary break-up. So I started with LES, and with a finer mesh, had the jet to break. I tried on a 2D mesh first (though not applicable to 2D, LES gave me very promising first results). I cannot keep up with the size of the mesh anymore in 3D, so am looking at the DES (SA) models OpenFOAM has. That should let me run coarser for the bulk flow without needing me to heavily resolve the near wall region. With the DES models, I will start using the wall functions as the near wall treatment is RANS.
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