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-   -   InterFoam channel Flow runnig very slowly (http://www.cfd-online.com/Forums/openfoam-solving/127664-interfoam-channel-flow-runnig-very-slowly.html)

Wokl December 17, 2013 04:52

InterFoam channel Flow runnig very slowly
 
1 Attachment(s)
Dear Foamers,

I am running a channel flow case using interfoam. In the beginning my sytem is filled with air and through an inlet water is transported to the system. It is a 3d case. A picture of the model is attached. I used the setfieldsdict for placing water at my inlet. I need to figure out how much water can run through my cahnnel without flooding (steady sate) and also the state while filling. I don't know if its running stable since in the last 24hours i just simulated 1 second.

I am not really experienced in CFD, so im learning and trying to get into it. therefore i hope i will be able to provide you enough information to get help.

I set up my case now in parallel using 2 processors in hope of speeding up a little. My checkmesh log is the log while running serial, but the mesh is the same. I generated my mesh using Salome.

Mesh: CheckMesh said it's ok

/*---------------------------------------------------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.2.2 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
Build : 2.2.2-9240f8b967db
Exec : checkMesh
Date : Dec 17 2013
Time : 08:51:23
Host : "christian-OptiPlex-780"
PID : 5957
Case : /home/christian/OpenFOAM/christian-2.2.2/FOAM_RUN/500
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 polyMesh for time = 0
Time = 0
Mesh stats
points: 104979
faces: 1060634
internal faces: 994814
cells: 513862
faces per cell: 4
boundary patches: 4
point zones: 0
face zones: 0
cell zones: 0
Overall number of cells of each type:
hexahedra: 0
prisms: 0
wedges: 0
pyramids: 0
tet wedges: 0
tetrahedra: 513862
polyhedra: 0
Checking topology...
Boundary definition OK.
Cell to face addressing OK.
Point usage OK.
Upper triangular ordering OK.
Face vertices OK.
Number of regions: 1 (OK).
Checking patch topology for multiply connected surfaces...
Patch Faces Points Surface topology
wall 51294 26517 ok (non-closed singly connected)
atmosphere 13881 7766 ok (non-closed singly connected)
outlet 242 145 ok (non-closed singly connected)
inlet 403 238 ok (non-closed singly connected)
Checking geometry...
Overall domain bounding box (-325.781 -157.3 0.235708) (-0.92 -7.2183 55.2)
Mesh (non-empty, non-wedge) directions (1 1 1)
Mesh (non-empty) directions (1 1 1)
Boundary openness (-3.60282e-16 4.79907e-16 -4.36398e-17) OK.
Max cell openness = 2.36045e-16 OK.
Max aspect ratio = 5.69515 OK.
Minimum face area = 5.88494e-05. Maximum face area = 1.09409. Face area magnitudes OK.
Min volume = 2.56612e-07. Max volume = 0.333882. Total volume = 998.721. Cell volumes OK.
Mesh non-orthogonality Max: 64.4178 average: 15.6647
Non-orthogonality check OK.
Face pyramids OK.
Max skewness = 0.972465 OK.
Coupled point location match (average 0) OK.
Mesh OK.
End

The boundary conditions are the same as matthew used (http://www.cfd-online.com/Forums/ope...wing-up-2.html) thx so far Matthew

I'm listing them anyway, i think its nicer to have the Info right here:

inlet: u_ fixed V
alpha_ fixed V 1
p_rgh_ bouyant
k,e fixed V

wall: u_fixed V
alpha_ zeroGradient
p_rgh_ bouyant
e,k_ wall Functions

outlet: u_ inletoutlet
alpha inletoutlet
p_rgh_ inletoutlet
e,k_ zeroGradient

atmosphere: u_pressureInletOutletVelocity
alpha_ inletOutlet
p_rgh_ totalPressure
e,k zeroGradient

Are these correct boundaries for my case?

The nbext thing of possible mistakes is, as i think my fv schemes. I started using the schemes from dambreak tutorial and changed then to the schemes matthew used, since his case worked. (thx again)

/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.2.2 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
location "system";
object fvSchemes;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
ddtSchemes
{
default Euler;
}
gradSchemes
{
default Gauss linear;
grad(U) cellLimited Gauss linear 1;
}
divSchemes
{
div(rho*phi,U) Gauss linearUpwindV grad(U);
div(phi,alpha) Gauss vanLeer;
div(phirb,alpha) Gauss interfaceCompression;
div(phi,k) Gauss upwind;
div(phi,epsilon) Gauss upwind;
div(phi,R) Gauss upwind;
div(R) Gauss linear;
div(phi,nuTilda) Gauss upwind;
div((muEff*dev(T(grad(U))))) Gauss linear;
}
laplacianSchemes
{
default Gauss linear corrected;
}
interpolationSchemes
{
default linear;
}
snGradSchemes
{
default corrected;
}
fluxRequired
{
default no;
p_rgh;
pcorr;
alpha;
}
 
// ************************************************** *********************** //

my fvsolution file:

/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.2.2 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
location "system";
object fvSolution;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
solvers
{
pcorr
{
solver PCG;
preconditioner DIC;
tolerance 1e-10;
relTol 0;
}
p_rgh
{
solver PCG;
preconditioner DIC;
tolerance 1e-07;
relTol 0.05;
}
p_rghFinal
{
solver PCG;
preconditioner DIC;
tolerance 1e-07;
relTol 0;
}
"(U|k|epsilon)"
{
solver PBiCG;
preconditioner DILU;
tolerance 1e-06;
relTol 0;
}
"(U|k|epsilon)Final"
{
solver PBiCG;
preconditioner DILU;
tolerance 1e-08;
relTol 0;
}
}
PIMPLE
{
momentumPredictor no;
nCorrectors 3;
nNonOrthogonalCorrectors 0;
nAlphaCorr 1;
nAlphaSubCycles 4;
cAlpha 1.0;
}
 
// ************************************************** *********************** //


My simulation log (parallel)

Courant Number mean: 0.000148995 max: 0.197988
Interface Courant Number mean: 3.44969e-06 max: 0.163836
deltaT = 0.00017807
Time = 0.00216492
MULES: Solving for alpha1
Phase-1 volume fraction = 0.000169865 Min(alpha1) = -1.39705e-19 Max(alpha1) = 1
MULES: Solving for alpha1
Phase-1 volume fraction = 0.000170311 Min(alpha1) = -1.28823e-19 Max(alpha1) = 1
DILUPBiCG: Solving for epsilon, Initial residual = 0.00070622, Final residual = 1.60462e-09, No Iterations 2
MULES: Solving for alpha1
Phase-1 volume fraction = 0.000170757 Min(alpha1) = -6.77334e-20 Max(alpha1) = 1
MULES: Solving for alpha1
Phase-1 volume fraction = 0.000171203 Min(alpha1) = -2.38929e-19 Max(alpha1) = 1
DILUPBiCG: Solving for k, Initial residual = 0.00353913, Final residual = 7.20539e-10, No Iterations 3
ExecutionTime = 567.26 s ClockTime = 597 s
Courant Number mean: 0.000148995 max: 0.197988
Interface Courant Number mean: 3.44969e-06 max: 0.163836
deltaT = 0.00017807
Time = 0.00216492
MULES: Solving for alpha1
Phase-1 volume fraction = 0.000169865 Min(alpha1) = -1.39705e-19 Max(alpha1) = 1
MULES: Solving for alpha1
Phase-1 volume fraction = 0.000170311 Min(alpha1) = -1.28823e-19 Max(alpha1) = 1
MULES: Solving for alpha1
Phase-1 volume fraction = 0.000170757 Min(alpha1) = -6.77334e-20 Max(alpha1) = 1
MULES: Solving for alpha1
Phase-1 volume fraction = 0.000171203 Min(alpha1) = -2.38929e-19 Max(alpha1) = 1
DICPCG: Solving for p_rgh, Initial residual = 0.00839266, Final residual = 0.000359386, No Iterations 3
time step continuity errors : sum local = 9.52655e-07, global = -4.18968e-11, cumulative = -3.01741e-06
DICPCG: Solving for p_rgh, Initial residual = 0.00839266, Final residual = 0.000359386, No Iterations 3
time step continuity errors : sum local = 9.52655e-07, global = -4.18968e-11, cumulative = -3.01741e-06
DICPCG: Solving for p_rgh, Initial residual = 0.00314155, Final residual = 0.000143956, No Iterations 4
time step continuity errors : sum local = 3.87928e-07, global = -5.3494e-11, cumulative = -3.01746e-06
DICPCG: Solving for p_rgh, Initial residual = 0.00314155, Final residual = 0.000143956, No Iterations 4
time step continuity errors : sum local = 3.87928e-07, global = -5.3494e-11, cumulative = -3.01746e-06
DICPCG: Solving for p_rgh, Initial residual = 0.000693082, Final residual = 9.16924e-08, No Iterations 101
time step continuity errors : sum local = 2.47532e-10, global = 4.23548e-11, cumulative = -3.01742e-06
DICPCG: Solving for p_rgh, Initial residual = 0.000693082, Final residual = 9.16924e-08, No Iterations 101
time step continuity errors : sum local = 2.47532e-10, global = 4.23548e-11, cumulative = -3.01742e-06
DILUPBiCG: Solving for epsilon, Initial residual = 0.000673068, Final residual = 1.37512e-09, No Iterations 2
DILUPBiCG: Solving for epsilon, Initial residual = 0.000673068, Final residual = 1.37512e-09, No Iterations 2
DILUPBiCG: Solving for k, Initial residual = 0.00333724, Final residual = 1.84395e-10, No Iterations 3
ExecutionTime = 597.69 s ClockTime = 629 s
Courant Number mean: 0.00014898 max: 0.198212
Interface Courant Number mean: 3.59589e-06 max: 0.1628
deltaT = 0.00017807
Time = 0.00234299
DILUPBiCG: Solving for k, Initial residual = 0.00333724, Final residual = 1.84395e-10, No Iterations 3
ExecutionTime = 598.01 s ClockTime = 630 s
Courant Number mean: 0.00014898 max: 0.198212
Interface Courant Number mean: 3.59589e-06 max: 0.1628
deltaT = 0.00017807
Time = 0.00234299
MULES: Solving for alpha1
Phase-1 volume fraction = 0.000171648 Min(alpha1) = -7.68723e-20 Max(alpha1) = 1
MULES: Solving for alpha1
Phase-1 volume fraction = 0.000171648 Min(alpha1) = -7.68723e-20 Max(alpha1) = 1
MULES: Solving for alpha1
Phase-1 volume fraction = 0.000172094 Min(alpha1) = -1.93227e-19 Max(alpha1) = 1
MULES: Solving for alpha1
Phase-1 volume fraction = 0.000172094 Min(alpha1) = -1.93227e-19 Max(alpha1) = 1
MULES: Solving for alpha1
Phase-1 volume fraction = 0.00017254 Min(alpha1) = -9.08318e-20 Max(alpha1) = 1
MULES: Solving for alpha1
MULES: Solving for alpha1
Phase-1 volume fraction = 0.000172986 Min(alpha1) = -1.54597e-19 Max(alpha1) = 1
Phase-1 volume fraction = 0.00017254 Min(alpha1) = -9.08318e-20 Max(alpha1) = 1
MULES: Solving for alpha1
Phase-1 volume fraction = 0.000172986 Min(alpha1) = -1.54597e-19 Max(alpha1) = 1
DICPCG: Solving for p_rgh, Initial residual = 0.00804302, Final residual = 0.000354484, No Iterations 3
DICPCG: Solving for p_rgh, Initial residual = 0.00804302, Final residual = 0.000354484, No Iterations 3
time step continuity errors : sum local = 9.48588e-07, global = 1.09394e-10, cumulative = -3.01731e-06
time step continuity errors : sum local = 9.48588e-07, global = 1.09394e-10, cumulative = -3.01731e-06
DICPCG: Solving for p_rgh, Initial residual = 0.00298146, Final residual = 0.000139001, No Iterations 4
time step continuity errors : sum local = 3.78049e-07, global = 9.93363e-11, cumulative = -3.01721e-06
DICPCG: Solving for p_rgh, Initial residual = 0.00298146, Final residual = 0.000139001, No Iterations 4
time step continuity errors : sum local = 3.78049e-07, global = 9.93363e-11, cumulative = -3.01721e-06
DICPCG: Solving for p_rgh, Initial residual = 0.000666371, Final residual = 9.9536e-08, No Iterations 109
time step continuity errors : sum local = 2.71273e-10, global = -4.12814e-11, cumulative = -3.01725e-06
DICPCG: Solving for p_rgh, Initial residual = 0.000666371, Final residual = 9.9536e-08, No Iterations 109
time step continuity errors : sum local = 2.71273e-10, global = -4.12814e-11, cumulative = -3.01725e-06
DILUPBiCG: Solving for epsilon, Initial residual = 0.000645486, Final residual = 1.19411e-09, No Iterations 2
DILUPBiCG: Solving for epsilon, Initial residual = 0.000645486, Final residual = 1.19411e-09, No Iterations 2
DILUPBiCG: Solving for k, Initial residual = 0.00316432, Final residual = 8.11749e-11, No Iterations 3
ExecutionTime = 629.65 s ClockTime = 664 s
Courant Number mean: 0.000148975 max: 0.198407
Interface Courant Number mean: 3.71594e-06 max: 0.161729
deltaT = 0.00017807
Time = 0.00252106
MULES: Solving for alpha1
Phase-1 volume fraction = 0.000173431 Min(alpha1) = -8.61642e-20 Max(alpha1) = 1
DILUPBiCG: Solving for k, Initial residual = 0.00316432, Final residual = 8.11749e-11, No Iterations 3
ExecutionTime = 629.28 s ClockTime = 666 s

Is it normal using this boundaries that the p_rgh field needs way more itartions than the other fields? Or is this specific to my model? Maybe i made here a Mistake? (Mesh? boundary?)


It has now simulated 0.11 seconds and it took 2350seconds real time.


The computer i'm using is a intelCore 2 3.00Ghz x2 with 4gb ram.

Thank u very much in advance
Christian

Wokl December 18, 2013 02:32

Hey Foamers,

i figured out, that running in parallel as i did it was useless. Just made the simulation slower.

Another thing what i wonder about is, are the boundary conditions for the outlet. The simulation stopped using the boundraries i mentioned in my last posting. by setting the outlet conditions equal to atmosphere (which in reality it is) it seems to be at least more stable.

Does anybody know, wheter my very slow simulation speed is due to my settings or my hardware?

thx
Christian

Wokl December 19, 2013 03:16

Hey,

i ran now into new Problems, maybe someone can help here. As seen on the picture in my first post, i expected the water phase to run down the channel. But somehow its trying pretty hard, i guess, not to run down and the level rises in the beginning of the tunnel.
Since i just have 500.000 cells and total length is about 400 meters, maybe its due to the resolution. Is that possible or was there another mistake made?

The other problem was that the simulation blew up after 3.6s. I think due to bounding epsilon. I changed my fvschemes now (http://www.cfd-online.com/Forums/ope...nvergence.html) and i will update when i get new results.

thx

Wokl December 22, 2013 06:08

So now i for sure, that the water doenst start flowing down the channel. Since this is a very new issue, i hope someone can help me here. I guess it has to be due to my settings of boundaries. the water starts flowing out to the atmosphere just the opposite direction of gravity. Do i have to set different condtions for my pressurre boundaries?

Thx

Wokl January 9, 2014 03:52

1 Attachment(s)
Dear Foamers,

I'm still hopelessly stuck on my problem. The pictures show the domain and i expected the water to flow down the channel as a water phase, at least water (alpha ~0.8) in the bottom of the channel. There is something flowing down the channel but not a very watery phase :(
These pictures are taken at 0; 0.3 and 1 seconds after start. If i keep simulating the water level rises in the very beginning.

Can somebody help me or give me a little hint?

Some other strange experience i made: i had to rotate my domain that everything was in y+ coordinates, otherwise nothing started to flow in direction of gravity (checked a 100 times). Had same problem having the higher parts of the domain (inlet) at a higher level of y than the lower parts, so gravity would point in -y. It seems like gravity is now "workling" but i would be also very thankful if someone knows this problem.


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