CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   OpenFOAM Running, Solving & CFD (http://www.cfd-online.com/Forums/openfoam-solving/)
-   -   same geometry,structured and unstructured mesh,different behaviour. (http://www.cfd-online.com/Forums/openfoam-solving/109953-same-geometry-structured-unstructured-mesh-different-behaviour.html)

sharonyue December 1, 2012 04:01

same geometry,structured and unstructured mesh,different behaviour.
 
1 Attachment(s)
Hi Foamers:

I use the same geometry but different mesh which one is structured and the other is unstructured simulating bubblecolumn via twoPhaseEulerFoam, the other things such as BCs,FVscheme is totally the same.
while running, the deltaT is getting smaller and smaller in unstructured mesh,but delta T is stable in structured mesh. I check the unstructured mesh is OK, and the quality is above 0.36.

can anybody explain this to me? thanks in advance.


Code:

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Create time

Create mesh for time = 0


Reading g
Reading transportProperties

Calculating face flux field phi1
Calculating face flux field phi2
Reading field alpha1

Reading field p

Reading field k

Reading field epsilon

Calculating field nut2

Calculating field nuEff1

Calculating field nuEff2

Calculating field DDtU1 and DDtU2

Calculating field g.h

Selecting dragModel for phase 1: SchillerNaumann
Selecting dragModel for phase 2: SchillerNaumann
dragPhase is 1
Selecting viscosityModel Syamlal
Selecting conductivityModel HrenyaSinclair
Selecting radialModel SinclairJackson
Selecting granularPressureModel Lun
Selecting frictionalStressModel JohnsonJackson
Courant Number mean: 1.38889e-06 max: 0.0114746

PIMPLE: Operating solver in PISO mode


Starting time loop

Courant Number mean: 1.37514e-06 max: 0.011361
Max Ur Courant Number = 0.011361
deltaT = 0.00235294
Time = 0.00235294

MULES: Solving for alpha1
MULES: Solving for alpha1
Dispersed phase volume fraction = 0.400913  Min(alpha1) = 0  Max(alpha1) = 1
GAMG:  Solving for p, Initial residual = 1, Final residual = 0.0863091, No Iterations 4
time step continuity errors : sum local = 1.06044e-05, global = -1.14961e-06, cumulative = -1.14961e-06
GAMG:  Solving for p, Initial residual = 0.000385431, Final residual = 4.25161e-09, No Iterations 8
time step continuity errors : sum local = 2.34062e-08, global = -8.86366e-09, cumulative = -1.15847e-06
ExecutionTime = 1.83 s  ClockTime = 2 s

Courant Number mean: 0.000961133 max: 0.281556
Max Ur Courant Number = 0.284771
deltaT = 0.0027451
Time = 0.00509804

MULES: Solving for alpha1
MULES: Solving for alpha1
Dispersed phase volume fraction = 0.400913  Min(alpha1) = -1.12164e-20  Max(alpha1) = 1
GAMG:  Solving for p, Initial residual = 8.63083e-05, Final residual = 4.00274e-06, No Iterations 1
time step continuity errors : sum local = 2.73396e-05, global = 2.22315e-06, cumulative = 1.06468e-06
GAMG:  Solving for p, Initial residual = 4.42412e-05, Final residual = 5.60681e-09, No Iterations 7
time step continuity errors : sum local = 4.22789e-08, global = 6.16051e-10, cumulative = 1.06529e-06
ExecutionTime = 3.15 s  ClockTime = 3 s

Courant Number mean: 0.0017551 max: 0.699786
Max Ur Courant Number = 0.556128
deltaT = 0.00194902
Time = 0.00704706

MULES: Solving for alpha1
MULES: Solving for alpha1
Dispersed phase volume fraction = 0.400913  Min(alpha1) = -6.81353e-17  Max(alpha1) = 1
GAMG:  Solving for p, Initial residual = 3.65894e-05, Final residual = 1.57627e-06, No Iterations 1
time step continuity errors : sum local = 5.16964e-06, global = -9.58478e-08, cumulative = 9.69446e-07
GAMG:  Solving for p, Initial residual = 5.6711e-05, Final residual = 6.50899e-09, No Iterations 6
time step continuity errors : sum local = 2.37495e-08, global = -3.80727e-09, cumulative = 9.65639e-07
ExecutionTime = 4.44 s  ClockTime = 5 s

Courant Number mean: 0.00167936 max: 1.02324
Max Ur Courant Number = 0.747501

deltaT = 1.99755e-06
Time = 0.00949938

MULES: Solving for alpha1
MULES: Solving for alpha1
Dispersed phase volume fraction = 0.400913  Min(alpha1) = -8.90338e-22  Max(alpha1) = 1
GAMG:  Solving for p, Initial residual = 0.0481777, Final residual = 0.00240455, No Iterations 1
time step continuity errors : sum local = 7.55737e-07, global = -8.0092e-10, cumulative = 8.87419e-07
GAMG:  Solving for p, Initial residual = 0.170165, Final residual = 5.99529e-09, No Iterations 14
time step continuity errors : sum local = 2.58254e-12, global = -1.71226e-13, cumulative = 8.87418e-07
ExecutionTime = 25.1 s  ClockTime = 25 s

Courant Number mean: 0.000246545 max: 0.954781
Max Ur Courant Number = 0.715363
deltaT = 1.04607e-06
Time = 0.00950043

MULES: Solving for alpha1
MULES: Solving for alpha1
Dispersed phase volume fraction = 0.400913  Min(alpha1) = -8.90337e-22  Max(alpha1) = 1
GAMG:  Solving for p, Initial residual = 0.0453175, Final residual = 0.00277426, No Iterations 1
time step continuity errors : sum local = 8.16799e-07, global = -3.74529e-10, cumulative = 8.87044e-07
GAMG:  Solving for p, Initial residual = 0.112757, Final residual = 4.36559e-09, No Iterations 14
time step continuity errors : sum local = 1.57546e-12, global = -1.38487e-13, cumulative = 8.87044e-07
ExecutionTime = 26.55 s  ClockTime = 27 s

Courant Number mean: 0.000191191 max: 0.775023
Max Ur Courant Number = 0.526832
deltaT = 6.74865e-07
Time = 0.0095011

MULES: Solving for alpha1
MULES: Solving for alpha1
Dispersed phase volume fraction = 0.400913  Min(alpha1) = -8.90337e-22  Max(alpha1) = 1
GAMG:  Solving for p, Initial residual = 0.0344062, Final residual = 0.00217738, No Iterations 1
time step continuity errors : sum local = 7.2002e-07, global = -5.49242e-10, cumulative = 8.86494e-07
GAMG:  Solving for p, Initial residual = 0.0678397, Final residual = 7.71205e-09, No Iterations 13
time step continuity errors : sum local = 2.89794e-12, global = -2.90138e-13, cumulative = 8.86494e-07
ExecutionTime = 28.17 s  ClockTime = 28 s

Courant Number mean: 0.000169 max: 0.691341
Max Ur Courant Number = 0.421516
deltaT = 4.88083e-07
Time = 0.00950159

MULES: Solving for alpha1
MULES: Solving for alpha1
Dispersed phase volume fraction = 0.400913  Min(alpha1) = -8.90337e-22  Max(alpha1) = 1
GAMG:  Solving for p, Initial residual = 0.0242849, Final residual = 0.00133999, No Iterations 1
time step continuity errors : sum local = 5.12642e-07, global = -7.3266e-10, cumulative = 8.85762e-07
GAMG:  Solving for p, Initial residual = 0.0466661, Final residual = 6.45613e-09, No Iterations 13
time step continuity errors : sum local = 2.72667e-12, global = -2.42677e-13, cumulative = 8.85761e-07
ExecutionTime = 29.69 s  ClockTime = 30 s

Courant Number mean: 0.00016667 max: 0.681466
Max Ur Courant Number = 0.389559
deltaT = 3.58113e-07
Time = 0.00950195

MULES: Solving for alpha1
MULES: Solving for alpha1
Dispersed phase volume fraction = 0.400913  Min(alpha1) = -8.90337e-22  Max(alpha1) = 1
GAMG:  Solving for p, Initial residual = 0.0275894, Final residual = 0.00152494, No Iterations 1
time step continuity errors : sum local = 6.50407e-07, global = -7.86185e-10, cumulative = 8.84975e-07
GAMG:  Solving for p, Initial residual = 0.048091, Final residual = 7.15538e-09, No Iterations 13
time step continuity errors : sum local = 3.39665e-12, global = -3.10169e-13, cumulative = 8.84975e-07
ExecutionTime = 31.21 s  ClockTime = 32 s

Courant Number mean: 0.000177114 max: 0.742118
Max Ur Courant Number = 0.434414
deltaT = 2.41277e-07
Time = 0.00950219

MULES: Solving for alpha1
MULES: Solving for alpha1
Dispersed phase volume fraction = 0.400913  Min(alpha1) = -8.90336e-22  Max(alpha1) = 1
GAMG:  Solving for p, Initial residual = 0.0434491, Final residual = 0.00265364, No Iterations 1
time step continuity errors : sum local = 1.17267e-06, global = -7.89578e-10, cumulative = 8.84185e-07
GAMG:  Solving for p, Initial residual = 0.0916966, Final residual = 4.20824e-09, No Iterations 14
time step continuity errors : sum local = 2.22575e-12, global = -2.16475e-13, cumulative = 8.84185e-07
ExecutionTime = 32.73 s  ClockTime = 33 s

Courant Number mean: 0.000201607 max: 0.927977
Max Ur Courant Number = 0.614956
deltaT = 1.30002e-07
Time = 0.00950232

MULES: Solving for alpha1
MULES: Solving for alpha1
Dispersed phase volume fraction = 0.400913  Min(alpha1) = -8.90336e-22  Max(alpha1) = 1
GAMG:  Solving for p, Initial residual = 0.0523101, Final residual = 0.00307465, No Iterations 1
time step continuity errors : sum local = 1.1458e-06, global = -7.83281e-10, cumulative = 8.83402e-07
GAMG:  Solving for p, Initial residual = 0.167959, Final residual = 6.72381e-09, No Iterations 14
time step continuity errors : sum local = 3.37666e-12, global = -1.97947e-13, cumulative = 8.83402e-07
ExecutionTime = 34.2 s  ClockTime = 34 s

Courant Number mean: 0.000213776 max: 1.09291
Max Ur Courant Number = 0.801885
deltaT = 5.94748e-08
Time = 0.00950238

MULES: Solving for alpha1
MULES: Solving for alpha1
Dispersed phase volume fraction = 0.400913  Min(alpha1) = -8.90336e-22  Max(alpha1) = 1
GAMG:  Solving for p, Initial residual = 0.0529512, Final residual = 0.00271119, No Iterations 1
time step continuity errors : sum local = 7.97202e-07, global = -7.88211e-10, cumulative = 8.82613e-07
GAMG:  Solving for p, Initial residual = 0.213293, Final residual = 8.38933e-09, No Iterations 14
time step continuity errors : sum local = 3.56226e-12, global = -1.41309e-13, cumulative = 8.82613e-07
ExecutionTime = 35.67 s  ClockTime = 36 s

Courant Number mean: 0.000203657 max: 1.09677
Max Ur Courant Number = 0.834422
deltaT = 2.71137e-08
Time = 0.0095024

MULES: Solving for alpha1
MULES: Solving for alpha1
Dispersed phase volume fraction = 0.400913  Min(alpha1) = -8.90336e-22  Max(alpha1) = 1
GAMG:  Solving for p, Initial residual = 0.0456457, Final residual = 0.00239763, No Iterations 1
time step continuity errors : sum local = 6.07151e-07, global = -6.76636e-10, cumulative = 8.81937e-07
GAMG:  Solving for p, Initial residual = 0.170025, Final residual = 7.23531e-09, No Iterations 14
time step continuity errors : sum local = 2.45147e-12, global = -1.08e-13, cumulative = 8.81936e-07
ExecutionTime = 37.23 s  ClockTime = 38 s

Courant Number mean: 0.000167332 max: 0.906812
Max Ur Courant Number = 0.660191
deltaT = 1.495e-08
Time = 0.00950242

MULES: Solving for alpha1
MULES: Solving for alpha1
Dispersed phase volume fraction = 0.400913  Min(alpha1) = -8.90336e-22  Max(alpha1) = 1
GAMG:  Solving for p, Initial residual = 0.0400672, Final residual = 0.00243865, No Iterations 1
time step continuity errors : sum local = 6.57129e-07, global = -5.7262e-10, cumulative = 8.81364e-07
GAMG:  Solving for p, Initial residual = 0.109301, Final residual = 4.88328e-09, No Iterations 14
time step continuity errors : sum local = 1.58805e-12, global = -1.09765e-13, cumulative = 8.81364e-07
ExecutionTime = 38.74 s  ClockTime = 39 s

Courant Number mean: 0.000143578 max: 0.769801
Max Ur Courant Number = 0.514251
deltaT = 9.7103e-09
Time = 0.00950243

--> FOAM Warning :
    From function Time::operator++()
    in file db/Time/Time.C at line 1024
    Increased the timePrecision from 6 to 7 to distinguish between timeNames at time 0.00950242
MULES: Solving for alpha1
MULES: Solving for alpha1
Dispersed phase volume fraction = 0.400913  Min(alpha1) = -8.90336e-22  Max(alpha1) = 1
GAMG:  Solving for p, Initial residual = 0.0301994, Final residual = 0.00188676, No Iterations 1
time step continuity errors : sum local = 5.87628e-07, global = -4.48811e-10, cumulative = 8.80915e-07
GAMG:  Solving for p, Initial residual = 0.0676315, Final residual = 8.08041e-09, No Iterations 13
time step continuity errors : sum local = 2.84689e-12, global = -3.41917e-13, cumulative = 8.80915e-07
ExecutionTime = 40.17 s  ClockTime = 40 s

Courant Number mean: 0.000133312 max: 0.69952
Max Ur Courant Number = 0.425703
deltaT = 6.94069e-09
Time = 0.009502436


jiez December 1, 2012 12:10

Usually, unstructured mesh is worse than structured mesh. There is a thread talking about the difference between unstructured mesh and structured mesh

http://www.cfd-online.com/Forums/cfx...ured-mesh.html

And the mesh quality depends on the meshing tool. Since you used auto adjusted delta T, when delta T getting smaller, it means the solution of flow has a trend to blow up. So I suggest using structured mesh if you can generate it.

Jie

sharonyue December 1, 2012 20:30

Quote:

Originally Posted by jiez (Post 395167)
Usually, unstructured mesh is worse than structured mesh. There is a thread talking about the difference between unstructured mesh and structured mesh

http://www.cfd-online.com/Forums/cfx...ured-mesh.html

And the mesh quality depends on the meshing tool. Since you used auto adjusted delta T, when delta T getting smaller, it means the solution of flow has a trend to blow up. So I suggest using structured mesh if you can generate it.

Jie

Thanks Jie, using structured mesh in a stirred tank is a tough job for me. except using structured mesh, is there anything else I can do to prevent the solution blowing up? such as fvscheme?

jiez December 2, 2012 14:09

Quote:

Originally Posted by sharonyue (Post 395224)
Thanks Jie, using structured mesh in a stirred tank is a tough job for me. except using structured mesh, is there anything else I can do to prevent the solution blowing up? such as fvscheme?

You mentioned you are modeling the flow in a stirred tank. I suppose you considered the stirrer in the flow as well. I have not much experience on dynamic mesh or MRF. BTW, are you using dynamic mesh or MRF?

To prevent blowing up, I would suggest you generally since I don't know detail about the solver you are using:
1. Reduce relaxation parameter.
2. Use up-wind scheme instead of central scheme;
3. Use scheme with lower-order accuracy;
4. Reduce the tolerance in FvSolution (The time spent on each iteration will be longer);
5. Use a better initial condition, such as the solution from run on structured mesh;
6. Try another meshing tool to generate unstructured mesh (Gmesh is disappointing on generating 3-D Mesh);
7. Try another solver is there are other alternatives.

Jie

The King December 2, 2012 15:10

Instead of moving mesh, you can define a source term with the average impuls of the stirror and apply it on the stirrer volume. The hex mesh should be possible.

sharonyue December 4, 2012 23:56

Quote:

Originally Posted by jiez (Post 395305)
You mentioned you are modeling the flow in a stirred tank. I suppose you considered the stirrer in the flow as well. I have not much experience on dynamic mesh or MRF. BTW, are you using dynamic mesh or MRF?

To prevent blowing up, I would suggest you generally since I don't know detail about the solver you are using:
1. Reduce relaxation parameter.
2. Use up-wind scheme instead of central scheme;
3. Use scheme with lower-order accuracy;
4. Reduce the tolerance in FvSolution (The time spent on each iteration will be longer);
5. Use a better initial condition, such as the solution from run on structured mesh;
6. Try another meshing tool to generate unstructured mesh (Gmesh is disappointing on generating 3-D Mesh);
7. Try another solver is there are other alternatives.

Jie

Thanks very much Jie, yeah I am using MRF, after I read your post , I tried some cases without consideration of MRF, just a tank filled with water injected with air.I used twoPhaseEulerFoam.or Bubblefoam.

in structured mesh. I got this result, that looks normal.

in unstructured mesh, in the fvscheme which is used in structured mesh, the delta T is getting too small, so I change the

div(phi1,alpha1) Gauss limitedLinearV 1;
div(phi2,alpha1) Gauss limitedLinearV 1;
to
div(phi,alpha1) Gauss upwind;
div(phir,alpha1) Gauss upwind;


just as expected, the solution didnot blow up. but the result is unrealistic:

I have alse tried reduce relaxation parameter and reduce the tolerance, but that did not have an impact to the unrealistic behaviour.

anyway, you are exactly correct about the modifying the fvscheme to prevent blowing up in an unstructured mesh, but how to handle this unrealistic behaviour?


now I have to use unstructured mesh, because I dont know how to set the structured mesh's inner face in ICEM. http://www.cfd-online.com/Forums/ope...tml#post395366

jiez December 5, 2012 16:32

If you start a run on unstructured mesh with a solution from structured mesh as initial condition, what's going to happen? Will it converge to a unrealistic solution or not?

sharonyue December 5, 2012 21:05

Quote:

Originally Posted by jiez (Post 396016)
If you start a run on unstructured mesh with a solution from structured mesh as initial condition, what's going to happen? Will it converge to a unrealistic solution or not?

Using the same geometry, If I generate a structured mesh at first, surely I can get a agreeable result, then if I generate a unstructured mesh and use the result of structured mesh, such as alpha or U at 0.001, I am afraid the total numbers are different with the structured mesh. so it looks like not plausible setting the nonuniform internal field.

do you mean this? anyway, thanks for your sustained help.

jiez December 6, 2012 11:18

You can use the openFoam utility: mapFields to map the solution from the structured mesh to unstructured mesh.

sharonyue December 7, 2012 00:06

I tryed mapfields,


Code:

patchMap        ( INLET INLET );
patchMap        ( OUTLET OUTLET );
patchMap        ( WALLS WALLS );
cuttingPatches  ( );

mapFileds works. and twophaseeulerfoam

Code:

/*---------------------------------------------------------------------------*\
| =========                |                                                |
| \\      /  F ield        | OpenFOAM: The Open Source CFD Toolbox          |
|  \\    /  O peration    | Version:  2.1.x                                |
|  \\  /    A nd          | Web:      www.OpenFOAM.org                      |
|    \\/    M anipulation  |                                                |
\*---------------------------------------------------------------------------*/
Build  : 2.1.x-6f9e6e8dbbf5
Exec  : twoPhaseEulerFoam
Date  : Dec 07 2012
Time  : 12:01:59
Host  : "cfd"
PID    : 2770
Case  : /home/cfd/OpenFOAM/tutorials/multiphase/twoPhaseEulerFoam/column/bubblecoloum2
nProcs : 1
sigFpe : Enabling floating point exception trapping (FOAM_SIGFPE).
fileModificationChecking : Monitoring run-time modified files using timeStampMaster
allowSystemOperations : Disallowing user-supplied system call operations

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Create time

Create mesh for time = 3.3


Reading g
Reading transportProperties

Calculating face flux field phi1
Calculating face flux field phi2
Reading field alpha1

Reading field p

Reading field k

Reading field epsilon

Calculating field nut2

Calculating field nuEff1

Calculating field nuEff2

Calculating field DDtU1 and DDtU2

Calculating field g.h

Selecting dragModel for phase 1: SchillerNaumann
Selecting dragModel for phase 2: SchillerNaumann
dragPhase is 1
Selecting viscosityModel Syamlal
Selecting conductivityModel HrenyaSinclair
Selecting radialModel SinclairJackson
Selecting granularPressureModel Lun
Selecting frictionalStressModel JohnsonJackson
Courant Number mean: 0.0352143 max: 0.72803

PIMPLE: Operating solver in PISO mode


Starting time loop

Courant Number mean: 0.0241194 max: 0.498651
Max Ur Courant Number = 0.383116
deltaT = 0.00136986
Time = 3.30137

MULES: Solving for alpha1
MULES: Solving for alpha1
Dispersed phase volume fraction = 0.299165  Min(alpha1) = 2.15895e-13  Max(alpha1) = 1.09964
GAMG:  Solving for p, Initial residual = 0.00656045, Final residual = 0.000298759, No Iterations 1
time step continuity errors : sum local = 0.000400447, global = 3.45188e-06, cumulative = 3.45188e-06
GAMG:  Solving for p, Initial residual = 0.000641632, Final residual = 5.89681e-09, No Iterations 17
time step continuity errors : sum local = 7.9181e-09, global = -6.00606e-09, cumulative = 3.44587e-06
ExecutionTime = 5.96 s  ClockTime = 6 s

Courant Number mean: 0.0248958 max: 0.585803
Max Ur Courant Number = 0.697338
deltaT = 0.000976536
Time = 3.30235

MULES: Solving for alpha1
MULES: Solving for alpha1
Dispersed phase volume fraction = 0.299163  Min(alpha1) = 2.2483e-13  Max(alpha1) = 1.08973
GAMG:  Solving for p, Initial residual = 0.00439207, Final residual = 0.000287956, No Iterations 1
time step continuity errors : sum local = 0.000169108, global = 4.09768e-07, cumulative = 3.85564e-06
GAMG:  Solving for p, Initial residual = 0.00109433, Final residual = 6.41174e-09, No Iterations 19
time step continuity errors : sum local = 3.74784e-09, global = -2.38899e-09, cumulative = 3.85325e-06
ExecutionTime = 9.81 s  ClockTime = 10 s

Courant Number mean: 0.0195134 max: 0.993167
Max Ur Courant Number = 1.04815
deltaT = 0.000465017
Time = 3.30281

MULES: Solving for alpha1
MULES: Solving for alpha1
Dispersed phase volume fraction = 0.299163  Min(alpha1) = 2.28675e-13  Max(alpha1) = 1.08657
GAMG:  Solving for p, Initial residual = 0.0110043, Final residual = 0.000779613, No Iterations 1
time step continuity errors : sum local = 0.000114244, global = 6.50821e-07, cumulative = 4.50407e-06
GAMG:  Solving for p, Initial residual = 0.00298644, Final residual = 8.64015e-09, No Iterations 15
time step continuity errors : sum local = 1.27991e-09, global = -9.74229e-10, cumulative = 4.5031e-06
ExecutionTime = 13.46 s  ClockTime = 13 s

Courant Number mean: 0.0107308 max: 1.58822
Max Ur Courant Number = 1.44814
deltaT = 0.000146368
Time = 3.30296

MULES: Solving for alpha1
MULES: Solving for alpha1
Dispersed phase volume fraction = 0.299163  Min(alpha1) = 2.28675e-13  Max(alpha1) = 1.08562
GAMG:  Solving for p, Initial residual = 0.0363906, Final residual = 0.00252655, No Iterations 1
time step continuity errors : sum local = 8.60275e-05, global = 1.47109e-06, cumulative = 5.97418e-06
GAMG:  Solving for p, Initial residual = 0.00697779, Final residual = 5.53144e-09, No Iterations 12
time step continuity errors : sum local = 1.94042e-10, global = 1.15085e-11, cumulative = 5.9742e-06
ExecutionTime = 16.94 s  ClockTime = 17 s

Courant Number mean: 0.00443779 max: 0.981418
Max Ur Courant Number = 0.957677
deltaT = 7.45332e-05
Time = 3.30303

MULES: Solving for alpha1
MULES: Solving for alpha1
Dispersed phase volume fraction = 0.299163  Min(alpha1) = 2.28675e-13  Max(alpha1) = 1.08493
GAMG:  Solving for p, Initial residual = 0.194527, Final residual = 0.011994, No Iterations 1
time step continuity errors : sum local = 7.45561e-05, global = 3.19653e-07, cumulative = 6.29385e-06
GAMG:  Solving for p, Initial residual = 0.0342165, Final residual = 6.34788e-09, No Iterations 14
time step continuity errors : sum local = 4.53813e-11, global = 2.84153e-11, cumulative = 6.29388e-06
ExecutionTime = 20.5 s  ClockTime = 20 s

Courant Number mean: 0.00321038 max: 1.91241
Max Ur Courant Number = 1.8986
deltaT = 1.94832e-05
Time = 3.30305

MULES: Solving for alpha1
MULES: Solving for alpha1
Dispersed phase volume fraction = 0.299163  Min(alpha1) = 2.28675e-13  Max(alpha1) = 1.0848
GAMG:  Solving for p, Initial residual = 0.66717, Final residual = 0.040409, No Iterations 1
time step continuity errors : sum local = 4.30358e-05, global = -2.37226e-07, cumulative = 6.05665e-06
GAMG:  Solving for p, Initial residual = 0.0749171, Final residual = 8.60659e-09, No Iterations 16
time step continuity errors : sum local = 1.46005e-11, global = 6.53075e-12, cumulative = 6.05666e-06
ExecutionTime = 24.22 s  ClockTime = 24 s

Courant Number mean: 0.00125969 max: 1.00435
Max Ur Courant Number = 1.00264
deltaT = 9.6987e-06
Time = 3.30306

MULES: Solving for alpha1
--> FOAM Warning :
    From function Time::operator++()
    in file db/Time/Time.C at line 1024
    Increased the timePrecision from 6 to 7 to distinguish between timeNames at time 3.30306
MULES: Solving for alpha1
Dispersed phase volume fraction = 0.299163  Min(alpha1) = 2.28675e-13  Max(alpha1) = 1.08472
GAMG:  Solving for p, Initial residual = 0.810231, Final residual = 0.0626473, No Iterations 1
time step continuity errors : sum local = 5.39472e-05, global = 2.64604e-07, cumulative = 6.32126e-06
GAMG:  Solving for p, Initial residual = 0.0977699, Final residual = 5.21597e-09, No Iterations 17
time step continuity errors : sum local = 7.02455e-12, global = 3.95107e-12, cumulative = 6.32126e-06
ExecutionTime = 28.02 s  ClockTime = 28 s

Courant Number mean: 0.00109578 max: 2.10824
Max Ur Courant Number = 1.4274
deltaT = 2.30017e-06
Time = 3.303064

MULES: Solving for alpha1
MULES: Solving for alpha1
Dispersed phase volume fraction = 0.299163  Min(alpha1) = 2.28675e-13  Max(alpha1) = 1.0847
GAMG:  Solving for p, Initial residual = 0.929304, Final residual = 0.0625062, No Iterations 1
time step continuity errors : sum local = 2.41344e-05, global = -4.81651e-08, cumulative = 6.2731e-06
GAMG:  Solving for p, Initial residual = 0.10263, Final residual = 5.41482e-09, No Iterations 18
time step continuity errors : sum local = 3.66151e-12, global = 2.58953e-12, cumulative = 6.2731e-06
ExecutionTime = 31.8 s  ClockTime = 32 s

Courant Number mean: 0.000505613 max: 0.757155
Max Ur Courant Number = 0.751618
deltaT = 1.51895e-06
Time = 3.303065

MULES: Solving for alpha1
--> FOAM Warning :
    From function Time::operator++()
    in file db/Time/Time.C at line 1024
    Increased the timePrecision from 7 to 8 to distinguish between timeNames at time 3.30307
MULES: Solving for alpha1
Dispersed phase volume fraction = 0.299163  Min(alpha1) = 2.28675e-13  Max(alpha1) = 1.0847
GAMG:  Solving for p, Initial residual = 0.812829, Final residual = 0.0712496, No Iterations 1
time step continuity errors : sum local = 3.64446e-05, global = 5.60153e-08, cumulative = 6.32912e-06
GAMG:  Solving for p, Initial residual = 0.105448, Final residual = 6.24808e-09, No Iterations 18
time step continuity errors : sum local = 4.86702e-12, global = 2.5297e-12, cumulative = 6.32912e-06
ExecutionTime = 35.67 s  ClockTime = 36 s

Courant Number mean: 0.000617812 max: 1.15822
Max Ur Courant Number = 0.973487
deltaT = 6.55726e-07
Time = 3.303066

MULES: Solving for alpha1
MULES: Solving for alpha1
Dispersed phase volume fraction = 0.299163  Min(alpha1) = 2.28675e-13  Max(alpha1) = 1.08469
GAMG:  Solving for p, Initial residual = 0.912736, Final residual = 0.0717027, No Iterations 1
time step continuity errors : sum local = 3.39342e-05, global = -5.31678e-08, cumulative = 6.27595e-06
GAMG:  Solving for p, Initial residual = 0.103759, Final residual = 8.11996e-09, No Iterations 16
time step continuity errors : sum local = 6.37729e-12, global = 3.39787e-12, cumulative = 6.27596e-06
ExecutionTime = 39.34 s  ClockTime = 39 s

Courant Number mean: 0.000524284 max: 1.3323
Max Ur Courant Number = 1.30873
deltaT = 2.46087e-07
Time = 3.3030662

MULES: Solving for alpha1
MULES: Solving for alpha1
Dispersed phase volume fraction = 0.299163  Min(alpha1) = 2.28675e-13  Max(alpha1) = 1.08468
GAMG:  Solving for p, Initial residual = 0.900043, Final residual = 0.0595418, No Iterations 1
time step continuity errors : sum local = 2.60454e-05, global = 1.05431e-07, cumulative = 6.38139e-06
GAMG:  Solving for p, Initial residual = 0.108187, Final residual = 7.39797e-09, No Iterations 17
time step continuity errors : sum local = 5.83461e-12, global = 2.75699e-12, cumulative = 6.38139e-06
ExecutionTime = 43.06 s  ClockTime = 43 s

Courant Number mean: 0.000461765 max: 1.72491
Max Ur Courant Number = 1.71906
deltaT = 7.13334e-08
Time = 3.3030663

MULES: Solving for alpha1
--> FOAM Warning :
    From function Time::operator++()
    in file db/Time/Time.C at line 1024
    Increased the timePrecision from 8 to 9 to distinguish between timeNames at time 3.30307

I have tried both the fvschemes:

1
Code:

ddtSchemes
{
    default        Euler;
}

gradSchemes
{
    default        Gauss linear;
}

divSchemes
{
    default        none;
    div(phi1,U1)    Gauss upwind;
    div(phi2,U2)    Gauss upwind;
    div(phi2,k)    Gauss upwind;
    div(phi2,epsilon) Gauss upwind;
    div(phi,alpha1)  Gauss upwind;
    div(phir,alpha1) Gauss limitedLinear01 1;
    div(phi,Theta)  Gauss upwind;
    div(Rc1)        Gauss linear;
    div(Rc2)        Gauss linear;
}

laplacianSchemes
{
    default        none;
    laplacian(nuEff1,U1) Gauss linear corrected;
    laplacian(nuEff2,U2) Gauss linear corrected;
    laplacian(Dp,p) Gauss linear corrected;
    laplacian(alpha1PpMag,alpha1) Gauss linear corrected;
    laplacian((alpha1k*nuEff2),k) Gauss linear corrected;
    laplacian((alpha1Eps*nuEff2),epsilon) Gauss linear corrected;
}

interpolationSchemes
{
    default        linear;
}

snGradSchemes
{
    default        corrected;
}

fluxRequired
{
    default        no;
    p              ;
}

2
Code:

ddtSchemes
{
    default        Euler;
}

gradSchemes
{
    default        Gauss linear;
}

divSchemes
{
    default        none;
    div(phi1,U1)    Gauss limitedLinearV 1;
    div(phi2,U2)    Gauss limitedLinearV 1;
    div(phi2,k)    Gauss limitedLinear 1;
    div(phi2,epsilon) Gauss limitedLinear 1;
    div(phi,alpha1)  Gauss limitedLinear01 1;
    div(phir,alpha1) Gauss limitedLinear01 1;
    div(phi,Theta)  Gauss limitedLinear 1;
    div(Rc1)        Gauss linear;
    div(Rc2)        Gauss linear;
}

laplacianSchemes
{
    default        none;
    laplacian(nuEff1,U1) Gauss linear corrected;
    laplacian(nuEff2,U2) Gauss linear corrected;
    laplacian(Dp,p) Gauss linear corrected;
    laplacian(alpha1PpMag,alpha1) Gauss linear corrected;
    laplacian((alpha1k*nuEff2),k) Gauss linear corrected;
    laplacian((alpha1Eps*nuEff2),epsilon) Gauss linear corrected;
}

interpolationSchemes
{
    default        linear;
}

snGradSchemes
{
    default        corrected;
}

fluxRequired
{
    default        no;
    p              ;
}



I am not sure this bubblefoam can work on an unstructured mesh.

sharonyue December 12, 2012 02:32

is there anyone doing the similar simulation?

sharonyue December 20, 2012 12:07

I am waiting for any suggestion...

bioexplore January 2, 2013 23:38

I want to simulate the same problem like you, but I am not quite sure about the boundary conditions for each variable, how did you set in your test case? Is boundary conditions have strong effects on the results?

sharonyue January 2, 2013 23:40

Quote:

Originally Posted by bioexplore (Post 399843)
I want to simulate the same problem like you, but I am not quite sure about the boundary conditions for each variable, how did you set in your test case? Is boundary conditions have strong effects on the results?

http://www.cfd-online.com/Forums/ope...tml#post397546 you can check this out.


All times are GMT -4. The time now is 20:16.