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-   -   two Phase column simulation (http://www.cfd-online.com/Forums/openfoam/75929-two-phase-column-simulation.html)

chemeng May 10, 2010 03:54

two Phase column simulation
 
3 Attachment(s)
Hello, I am trying to simulate a two phase (air-water) column. Initially, there is water in the column until the level of 450 mm and the rest is air. Only air is injecting in the column through the bottom of it. My overall domain is (0 0 0) (200 700 50). I have used setFields to set the initial water level as follows:
defaultFieldValues
(
volScalarFieldValue alpha 1
);


regions
(
boxToCell
{
box (0 0 0) (200 450 50);
fieldValues
(
volScalarFieldValue alpha 0
);
}
);

I attach here the 0, constant and system directories. This case is similar to the bubble plume case in Henrik Rusche tesis. I have used twoPhaseEulerFoam to solve it, but always the solver fails. These are the last steps of my simulation:
Time = 0.791

DILUPBiCG: Solving for alpha, Initial residual = 2.63349e-07, Final residual = 1.86978e-16, No Iterations 1
Dispersed phase volume fraction = 0.349989 Min(alpha) = -2.24462e-10 Max(alpha) = 1
DILUPBiCG: Solving for alpha, Initial residual = 4.74634e-11, Final residual = 4.74634e-11, No Iterations 0
Dispersed phase volume fraction = 0.349989 Min(alpha) = -2.24462e-10 Max(alpha) = 1
GAMG: Solving for p, Initial residual = 0.986187, Final residual = 5.73366e-09, No Iterations 17
time step continuity errors : sum local = 1.40345e-05, global = 1.79727e-07, cumulative = 2.10044e-05
GAMG: Solving for p, Initial residual = 1.22598e-05, Final residual = 3.53858e-09, No Iterations 8
time step continuity errors : sum local = 1.77695e-08, global = 1.40128e-08, cumulative = 2.10184e-05
DILUPBiCG: Solving for epsilon, Initial residual = 0.56183, Final residual = 5.35533e-06, No Iterations 2
DILUPBiCG: Solving for k, Initial residual = 1, Final residual = 4.04759e-06, No Iterations 19
ExecutionTime = 246.88 s ClockTime = 276 s

Courant Number mean: 2.94236e-06 max: 9.39065e-05
Max Ur Courant Number = 0.000103406
Calculating averages

Time = 0.792

DILUPBiCG: Solving for alpha, Initial residual = 2.07051e-07, Final residual = 1.18426e-16, No Iterations 1
Dispersed phase volume fraction = 0.349989 Min(alpha) = -2.24444e-10 Max(alpha) = 1
DILUPBiCG: Solving for alpha, Initial residual = 4.87669e-12, Final residual = 4.87669e-12, No Iterations 0
Dispersed phase volume fraction = 0.349989 Min(alpha) = -2.24444e-10 Max(alpha) = 1
GAMG: Solving for p, Initial residual = 0.99911, Final residual = 1.62335e-09, No Iterations 16
time step continuity errors : sum local = 4.85304e-07, global = -6.78739e-08, cumulative = 2.09505e-05
GAMG: Solving for p, Initial residual = 1.22245e-07, Final residual = 4.05677e-09, No Iterations 3
time step continuity errors : sum local = 4.3112e-08, global = 2.02119e-08, cumulative = 2.09707e-05
DILUPBiCG: Solving for epsilon, Initial residual = 0.387714, Final residual = 9.80831e-06, No Iterations 8
DILUPBiCG: Solving for k, Initial residual = 1, Final residual = 7.55652e-06, No Iterations 9
ExecutionTime = 247.3 s ClockTime = 276 s

Courant Number mean: 2.86588e-06 max: 8.43784e-05
Max Ur Courant Number = 8.57354e-05
Calculating averages

Time = 0.793

DILUPBiCG: Solving for alpha, Initial residual = 2.24368e-07, Final residual = 1.04551e-16, No Iterations 1
Dispersed phase volume fraction = 0.349989 Min(alpha) = -2.24425e-10 Max(alpha) = 1
DILUPBiCG: Solving for alpha, Initial residual = 8.27431e-12, Final residual = 8.27431e-12, No Iterations 0
Dispersed phase volume fraction = 0.349989 Min(alpha) = -2.24425e-10 Max(alpha) = 1
GAMG: Solving for p, Initial residual = 0.995351, Final residual = 3.11721e-09, No Iterations 14
time step continuity errors : sum local = 3.67949e-06, global = 1.30844e-06, cumulative = 2.22792e-05
GAMG: Solving for p, Initial residual = 2.60418e-14, Final residual = 2.60418e-14, No Iterations 0
time step continuity errors : sum local = 4.57825e-06, global = 1.30906e-06, cumulative = 2.35882e-05
DILUPBiCG: Solving for epsilon, Initial residual = 0.872664, Final residual = 3.49504e-06, No Iterations 11
DILUPBiCG: Solving for k, Initial residual = 1, Final residual = 6.70844e-06, No Iterations 3
ExecutionTime = 247.69 s ClockTime = 277 s

Courant Number mean: 7.98444e-06 max: 0.000214576
Max Ur Courant Number = 0.000246573
Calculating averages

Time = 0.794

DILUPBiCG: Solving for alpha, Initial residual = 5.0522e-06, Final residual = 2.6061e-15, No Iterations 1
Dispersed phase volume fraction = 0.349988 Min(alpha) = -2.24409e-10 Max(alpha) = 1.00007
DILUPBiCG: Solving for alpha, Initial residual = 3.6218e-10, Final residual = 2.19924e-19, No Iterations 1
Dispersed phase volume fraction = 0.349988 Min(alpha) = -2.24409e-10 Max(alpha) = 1.00007
GAMG: Solving for p, Initial residual = 0.99362, Final residual = 2.91436e-09, No Iterations 19
time step continuity errors : sum local = 79.1722, global = -45.1975, cumulative = -45.1975
GAMG: Solving for p, Initial residual = 8.58661e-06, Final residual = 8.05537e-09, No Iterations 10
time step continuity errors : sum local = 0.0754832, global = 0.0614776, cumulative = -45.136
DILUPBiCG: Solving for epsilon, Initial residual = 0.333104, Final residual = 4.24405e-06, No Iterations 285
DILUPBiCG: Solving for k, Initial residual = 0.98362, Final residual = 1.79691, No Iterations 1001
ExecutionTime = 250.35 s ClockTime = 279 s

Courant Number mean: 2.9945 max: 496.215
Max Ur Courant Number = 712.315
Calculating averages

Time = 0.795

DILUPBiCG: Solving for alpha, Initial residual = 0.305668, Final residual = 8.34833e-11, No Iterations 40
Dispersed phase volume fraction = 0.308743 Min(alpha) = -10.9055 Max(alpha) = 19.6875
DILUPBiCG: Solving for alpha, Initial residual = 0.950365, Final residual = 6.24853e-11, No Iterations 124
Dispersed phase volume fraction = 0.148458 Min(alpha) = -29.0766 Max(alpha) = 17.1806

Any help is appreciated. Thanks in advance.

gwierink June 18, 2010 04:00

Hi Benjamin,

Sorry for this late reply, perhaps you have solved it already, but if not I'll try to help.

I downloaded your case files, but can't find the actual mesh. Is it just a rectangular column? If so, blockMesh will work fine.


Quote:

defaultFieldValues
(
volScalarFieldValue alpha 1
);


regions
(
boxToCell
{
box (0 0 0) (200 450 50);
fieldValues
(
volScalarFieldValue alpha 0
);
}
);
Here you set a "chunk" of water above a layer of air, which will the collapse, am I right? Do you really want that? I mean, isn't it better to start a bubble column from a column of water and then blow in air?

Have you tried to simply modify the bubbleCollumn tutorials for twoPhaseEulerFoam?

soccol August 18, 2010 12:41

two Phase column simulation
 
Benjamin,

I had the same problem then you, but my gas-liquid system is little different, is a cylindrical column, this problem was solved.

so...apply a relaxation factor to the firstly seconds in your simulation on the k and epsilon variable, about 0.9 for both, on the /system/fvsolution like this.

sorry about my English.


/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 1.6 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
location "system";
object fvSolution;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

solvers
{
p
{
solver GAMG;
tolerance 1e-08;
relTol 0;
smoother DIC;
nPreSweeps 0;
nPostSweeps 2;
nFinestSweeps 2;
cacheAgglomeration true;
nCellsInCoarsestLevel 10;
agglomerator faceAreaPair;
mergeLevels 1;
}

Ua
{
solver PBiCG;
preconditioner DILU;
tolerance 1e-05;
relTol 0;
}

Ub
{
solver PBiCG;
preconditioner DILU;
tolerance 1e-05;
relTol 0;
}

alpha
{
solver PBiCG;
preconditioner DILU;
tolerance 1e-10;
relTol 0;
}

beta
{
solver PBiCG;
preconditioner DILU;
tolerance 1e-10;
relTol 0;
}

Theta
{
solver PBiCG;
preconditioner DILU;
tolerance 1e-05;
relTol 0;
}

k
{
solver PBiCG;
preconditioner DILU;
tolerance 1e-05;
relTol 0;
}

epsilon
{
solver PBiCG;
preconditioner DILU;
tolerance 1e-05;
relTol 0;
}
}

PISO
{
nCorrectors 3;
nNonOrthogonalCorrectors 0;
nAlphaCorr 3;
correctAlpha no;
pRefCell 0;
pRefValue 0;
}

relaxationFactors
{
Ua 1;
Ub 1;
alpha 1;
beta 1;
Theta 1;
k 0.9;
epsilon 0.9;
}
// ************************************************** *********************** //

soccol August 18, 2010 12:53

setFields
 
their alpha initial conditions are correct. Alpha 0 means that there is water up to 450 and after that, alpha 1, only air is present on the column.


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