# same geometry,structured and unstructured mesh,different behaviour.

 Register Blogs Members List Search Today's Posts Mark Forums Read December 1, 2012, 03:01 same geometry,structured and unstructured mesh,different behaviour.
#1
Senior Member

Dongyue Li
Join Date: Jun 2012
Location: Beijing, China
Posts: 784
Rep Power: 14 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

Calculating face flux field phi1
Calculating face flux field phi2

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 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```
Attached Files log.zip (5.2 KB, 18 views)

Last edited by sharonyue; December 1, 2012 at 03:48.   December 1, 2012, 11:10 #2 New Member   Jie (Jay) Zhang Join Date: Sep 2010 Location: Seattle, WA, U.S. Posts: 27 Rep Power: 13 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   December 1, 2012, 19:30 #3
Senior Member

Dongyue Li
Join Date: Jun 2012
Location: Beijing, China
Posts: 784
Rep Power: 14 Quote:
 Originally Posted by jiez 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?   December 2, 2012, 13:09 #4
New Member

Jie (Jay) Zhang
Join Date: Sep 2010
Location: Seattle, WA, U.S.
Posts: 27
Rep Power: 13 Quote:
 Originally Posted by sharonyue 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   December 2, 2012, 14:10 #5 Member   Arnout Join Date: Nov 2010 Posts: 46 Rep Power: 12 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.   December 4, 2012, 22:56 #6
Senior Member

Dongyue Li
Join Date: Jun 2012
Location: Beijing, China
Posts: 784
Rep Power: 14 Quote:
 Originally Posted by jiez 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   December 5, 2012, 15:32 #7 New Member   Jie (Jay) Zhang Join Date: Sep 2010 Location: Seattle, WA, U.S. Posts: 27 Rep Power: 13 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?   December 5, 2012, 20:05 #8
Senior Member

Dongyue Li
Join Date: Jun 2012
Location: Beijing, China
Posts: 784
Rep Power: 14 Quote:
 Originally Posted by jiez 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.   December 6, 2012, 10:18 #9 New Member   Jie (Jay) Zhang Join Date: Sep 2010 Location: Seattle, WA, U.S. Posts: 27 Rep Power: 13 You can use the openFoam utility: mapFields to map the solution from the structured mesh to unstructured mesh.   December 6, 2012, 23:06 #10 Senior Member   Dongyue Li Join Date: Jun 2012 Location: Beijing, China Posts: 784 Rep Power: 14 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.   December 12, 2012, 01:32 #11 Senior Member   Dongyue Li Join Date: Jun 2012 Location: Beijing, China Posts: 784 Rep Power: 14 is there anyone doing the similar simulation？   December 20, 2012, 11:07 #12 Senior Member   Dongyue Li Join Date: Jun 2012 Location: Beijing, China Posts: 784 Rep Power: 14 I am waiting for any suggestion...   January 2, 2013, 22:38 #13 Member   Jianye Xia Join Date: Mar 2009 Posts: 32 Rep Power: 15 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?   January 2, 2013, 22:40 #14
Senior Member

Dongyue Li
Join Date: Jun 2012
Location: Beijing, China
Posts: 784
Rep Power: 14 Quote:
 Originally Posted by bioexplore 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.  Thread Tools Search this Thread Show Printable Version Email this Page Search this Thread: Advanced Search Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are Off Pingbacks are On Refbacks are On Forum Rules Similar Threads Thread Thread Starter Forum Replies Last Post psosnows OpenFOAM Bugs 4 October 19, 2011 15:48 didiean FLUENT 11 April 3, 2011 02:10 user Main CFD Forum 6 November 25, 2010 01:14 moomba Main CFD Forum 0 February 25, 2010 15:38 APURVA SHUKLA Main CFD Forum 2 March 15, 2001 00:14

All times are GMT -4. The time now is 13:59.