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a problem with convergence in buoyantSimpleFoam

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Old   January 16, 2014, 14:47
Default a problem with convergence in buoyantSimpleFoam
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Sergey
Join Date: Nov 2013
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Hello!

I'm trying to solve a problem of a flow through a complex geometry(picture is attached).
I was able to mesh my stl geometry and set up the case in HelyxOS. However, when I am trying to solve it with buoyantSimpleFoam, there is no convergence: the residuals start oscillating. Probably it is because of complex geometry. I had the similar problem why I was trying to solve this case in abaqus and i hoped that OpenFOAM will be better, but got the same problem.

log:
Code:
case = /home/sergkuznet/Engys/HELYX-OS/v2.0.0/UCfluidsmall_meshed_compressible
log = /home/sergkuznet/Engys/HELYX-OS/v2.0.0/UCfluidsmall_meshed_compressible/log/buoyantSimpleFoam.log
solver = buoyantSimpleFoam
vendorHome = /opt
environmentLoader = /opt/openfoam222/etc/bashrc
/*---------------------------------------------------------------------------*\
| =========                 |                                                 |
| \\      /  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   : buoyantSimpleFoam -case /home/sergkuznet/Engys/HELYX-OS/v2.0.0/UCfluidsmall_meshed_compressible
Date   : Jan 15 2014
Time   : 23:30:58
Host   : "ubuntu"
PID    : 24661
Case   : /home/sergkuznet/Engys/HELYX-OS/v2.0.0/UCfluidsmall_meshed_compressible
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 = 0


Reading g
Reading thermophysical properties

Selecting thermodynamics package 
{
    type            heRhoThermo;
    mixture         pureMixture;
    transport       const;
    thermo          hConst;
    equationOfState perfectGas;
    specie          specie;
    energy          sensibleEnthalpy;
}

Reading field U

Reading/calculating face flux field phi

Creating turbulence model

Selecting RAS turbulence model kEpsilon
kEpsilonCoeffs
{
    label           "Standard high-Re k-\u03B5";
    fieldMaps
    {
        k               kCompressible;
        epsilon         epsilonCompressible;
        mut             mut;
        alphat          alphatCompressible;
    }
    Cmu             0.09;
    C1              1.44;
    C2              1.92;
    C3              0.85;
    alphah          1.111;
    alphak          1;
    alphaEps        0.76923;
    sigmak          1;
    sigmaEps        1.3;
    Prt             1;
}

Calculating field g.h

Reading field p_rgh

Creating fintite volume options from fvOptions

Radiation model not active: radiationProperties not found
Selecting radiationModel none

SIMPLE: no convergence criteria found. Calculations will run for 50000 steps.


Starting time loop

Time = 1

smoothSolver:  Solving for Ux, Initial residual = 1, Final residual = 0.05456998525, No Iterations 2
smoothSolver:  Solving for Uy, Initial residual = 1, Final residual = 0.04761354967, No Iterations 2
smoothSolver:  Solving for Uz, Initial residual = 1, Final residual = 0.0923876983, No Iterations 2
smoothSolver:  Solving for h, Initial residual = 0.9999999996, Final residual = 0.02860158267, No Iterations 3
GAMG:  Solving for p_rgh, Initial residual = 0.882758416, Final residual = 0.03173471025, No Iterations 4
time step continuity errors : sum local = 0.005249873879, global = -0.000182711125, cumulative = -0.000182711125
rho max/min : 1.158622649 1.142785577
smoothSolver:  Solving for epsilon, Initial residual = 0.1608057626, Final residual = 0.006153099236, No Iterations 2
smoothSolver:  Solving for k, Initial residual = 1, Final residual = 0.03719092912, No Iterations 3
ExecutionTime = 4.76 s  ClockTime = 4 s

Time = 2

smoothSolver:  Solving for Ux, Initial residual = 0.7259532586, Final residual = 0.02361427294, No Iterations 3
smoothSolver:  Solving for Uy, Initial residual = 0.7068399159, Final residual = 0.02238854075, No Iterations 3
smoothSolver:  Solving for Uz, Initial residual = 0.6699165409, Final residual = 0.02056174524, No Iterations 3
smoothSolver:  Solving for h, Initial residual = 0.7405307436, Final residual = 0.02051199796, No Iterations 3
GAMG:  Solving for p_rgh, Initial residual = 0.304082482, Final residual = 0.01050962275, No Iterations 7
time step continuity errors : sum local = 0.1774290497, global = 0.001030155269, cumulative = 0.0008474441436
rho max/min : 1.158650312 1.13997601
smoothSolver:  Solving for epsilon, Initial residual = 0.01048787725, Final residual = 0.000319066845, No Iterations 2
smoothSolver:  Solving for k, Initial residual = 0.7883387769, Final residual = 0.04988614677, No Iterations 2
ExecutionTime = 7.4 s  ClockTime = 7 s

Time = 3

smoothSolver:  Solving for Ux, Initial residual = 0.3011829881, Final residual = 0.00895536283, No Iterations 3
smoothSolver:  Solving for Uy, Initial residual = 0.3393492916, Final residual = 0.03275950006, No Iterations 2
smoothSolver:  Solving for Uz, Initial residual = 0.2385413804, Final residual = 0.007124100008, No Iterations 3
smoothSolver:  Solving for h, Initial residual = 0.2914052321, Final residual = 0.01625010492, No Iterations 2
GAMG:  Solving for p_rgh, Initial residual = 0.8042185927, Final residual = 0.02773146053, No Iterations 4
time step continuity errors : sum local = 0.1888755073, global = 0.006418408439, cumulative = 0.007265852582
rho max/min : 1.15968521 1.137278596
smoothSolver:  Solving for epsilon, Initial residual = 0.01144151224, Final residual = 0.0003601066569, No Iterations 2
smoothSolver:  Solving for k, Initial residual = 0.08325549938, Final residual = 0.00442307674, No Iterations 2
ExecutionTime = 9.86 s  ClockTime = 9 s

Time = 4

smoothSolver:  Solving for Ux, Initial residual = 0.3572870107, Final residual = 0.01098460154, No Iterations 3
smoothSolver:  Solving for Uy, Initial residual = 0.3412253921, Final residual = 0.01018265882, No Iterations 3
smoothSolver:  Solving for Uz, Initial residual = 0.1938818624, Final residual = 0.00590410665, No Iterations 3
smoothSolver:  Solving for h, Initial residual = 0.06609471347, Final residual = 0.004228284277, No Iterations 2
GAMG:  Solving for p_rgh, Initial residual = 0.4711994431, Final residual = 0.02294413812, No Iterations 4
time step continuity errors : sum local = 0.2498850098, global = 0.00713703493, cumulative = 0.01440288751
rho max/min : 1.162113569 1.134617233
smoothSolver:  Solving for epsilon, Initial residual = 0.01412601771, Final residual = 0.000576026232, No Iterations 2
smoothSolver:  Solving for k, Initial residual = 0.05042717657, Final residual = 0.003666382958, No Iterations 2
ExecutionTime = 12.28 s  ClockTime = 12 s
...

Code:
Time = 6893

smoothSolver:  Solving for Ux, Initial residual = 0.001109267103, Final residual = 9.301950987e-05, No Iterations 2
smoothSolver:  Solving for Uy, Initial residual = 0.002552499345, Final residual = 0.0002171982442, No Iterations 2
smoothSolver:  Solving for Uz, Initial residual = 0.001721074846, Final residual = 0.0001393752654, No Iterations 2
smoothSolver:  Solving for h, Initial residual = 0.001774111589, Final residual = 0.0001480908181, No Iterations 2
GAMG:  Solving for p_rgh, Initial residual = 0.02942919705, Final residual = 0.001007022019, No Iterations 2
time step continuity errors : sum local = 0.006661556709, global = -1.051356534e-05, cumulative = 0.0100249542
rho max/min : 1.555319782 1.028572963
smoothSolver:  Solving for epsilon, Initial residual = 0.0006588752087, Final residual = 3.222172574e-05, No Iterations 2
smoothSolver:  Solving for k, Initial residual = 0.001165457605, Final residual = 7.263342197e-05, No Iterations 2
ExecutionTime = 15783.15 s  ClockTime = 15811 s

Time = 6894

smoothSolver:  Solving for Ux, Initial residual = 0.001105061853, Final residual = 9.282106832e-05, No Iterations 2
smoothSolver:  Solving for Uy, Initial residual = 0.002539850795, Final residual = 0.0002170841452, No Iterations 2
smoothSolver:  Solving for Uz, Initial residual = 0.001712852001, Final residual = 0.0001392339211, No Iterations 2
smoothSolver:  Solving for h, Initial residual = 0.001768589731, Final residual = 0.0001480461638, No Iterations 2
GAMG:  Solving for p_rgh, Initial residual = 0.02919360825, Final residual = 0.0009926483288, No Iterations 2
time step continuity errors : sum local = 0.006562854633, global = -3.20007918e-05, cumulative = 0.009992953411
rho max/min : 1.555999036 1.028541909
smoothSolver:  Solving for epsilon, Initial residual = 0.0006562511602, Final residual = 3.206656798e-05, No Iterations 2
smoothSolver:  Solving for k, Initial residual = 0.001165405109, Final residual = 7.245995858e-05, No Iterations 2
ExecutionTime = 15785.4 s  ClockTime = 15814 s

Time = 6895

smoothSolver:  Solving for Ux, Initial residual = 0.00109332315, Final residual = 9.182453762e-05, No Iterations 2
smoothSolver:  Solving for Uy, Initial residual = 0.002532421163, Final residual = 0.0002170932441, No Iterations 2
smoothSolver:  Solving for Uz, Initial residual = 0.001705007101, Final residual = 0.0001390125982, No Iterations 2
smoothSolver:  Solving for h, Initial residual = 0.001764165224, Final residual = 0.0001480728942, No Iterations 2
GAMG:  Solving for p_rgh, Initial residual = 0.0289295584, Final residual = 0.000999707326, No Iterations 2
time step continuity errors : sum local = 0.006605380848, global = -9.827082398e-06, cumulative = 0.009983126328
rho max/min : 1.557878892 1.028510636
smoothSolver:  Solving for epsilon, Initial residual = 0.0006530257994, Final residual = 3.188133514e-05, No Iterations 2
smoothSolver:  Solving for k, Initial residual = 0.001162685421, Final residual = 7.23104506e-05, No Iterations 2
ExecutionTime = 15787.71 s  ClockTime = 15816 s
....

Code:
Time = 13613

smoothSolver:  Solving for Ux, Initial residual = 0.0005045956734, Final residual = 4.340934053e-05, No Iterations 2
smoothSolver:  Solving for Uy, Initial residual = 0.001157194444, Final residual = 0.0001049946357, No Iterations 2
smoothSolver:  Solving for Uz, Initial residual = 0.000840632502, Final residual = 7.075824151e-05, No Iterations 2
smoothSolver:  Solving for h, Initial residual = 0.0008323391129, Final residual = 7.193982016e-05, No Iterations 2
GAMG:  Solving for p_rgh, Initial residual = 0.01360653861, Final residual = 0.0004963259508, No Iterations 2
time step continuity errors : sum local = 0.003249437982, global = 3.573092127e-05, cumulative = 0.01659601022
rho max/min : 1.620925196 1.026426236
smoothSolver:  Solving for epsilon, Initial residual = 0.0003452632898, Final residual = 1.733068307e-05, No Iterations 2
smoothSolver:  Solving for k, Initial residual = 0.0005906923144, Final residual = 4.027091396e-05, No Iterations 2
ExecutionTime = 31148.92 s  ClockTime = 31204 s

Time = 13614

smoothSolver:  Solving for Ux, Initial residual = 0.000506167618, Final residual = 4.357008435e-05, No Iterations 2
smoothSolver:  Solving for Uy, Initial residual = 0.001159136638, Final residual = 0.0001051976481, No Iterations 2
smoothSolver:  Solving for Uz, Initial residual = 0.0008379983297, Final residual = 7.044233602e-05, No Iterations 2
smoothSolver:  Solving for h, Initial residual = 0.0008271563341, Final residual = 7.156204547e-05, No Iterations 2
GAMG:  Solving for p_rgh, Initial residual = 0.01359108374, Final residual = 0.0004953122914, No Iterations 2
time step continuity errors : sum local = 0.003242773843, global = 3.226945802e-05, cumulative = 0.01662827968
rho max/min : 1.621060156 1.026379888
smoothSolver:  Solving for epsilon, Initial residual = 0.0003443170465, Final residual = 1.723312939e-05, No Iterations 2
smoothSolver:  Solving for k, Initial residual = 0.0005895732474, Final residual = 4.006604868e-05, No Iterations 2
ExecutionTime = 31151.27 s  ClockTime = 31206 s


Code:
Time = 18885

smoothSolver:  Solving for Ux, Initial residual = 0.0006130175635, Final residual = 4.984637275e-05, No Iterations 2
smoothSolver:  Solving for Uy, Initial residual = 0.00146555805, Final residual = 0.0001198237563, No Iterations 2
smoothSolver:  Solving for Uz, Initial residual = 0.001049220622, Final residual = 8.563853344e-05, No Iterations 2
smoothSolver:  Solving for h, Initial residual = 0.001103103009, Final residual = 9.056864292e-05, No Iterations 2
GAMG:  Solving for p_rgh, Initial residual = 0.01792917561, Final residual = 0.0006453816647, No Iterations 2
time step continuity errors : sum local = 0.004211850033, global = -4.69373984e-05, cumulative = 0.02838930114
rho max/min : 1.61685718 1.027702955
smoothSolver:  Solving for epsilon, Initial residual = 0.0003757520635, Final residual = 1.640617344e-05, No Iterations 2
smoothSolver:  Solving for k, Initial residual = 0.0006832165346, Final residual = 4.135313509e-05, No Iterations 2
ExecutionTime = 43243.93 s  ClockTime = 43321 s

Time = 18886

smoothSolver:  Solving for Ux, Initial residual = 0.0006085962287, Final residual = 4.947465059e-05, No Iterations 2
smoothSolver:  Solving for Uy, Initial residual = 0.001453701216, Final residual = 0.0001189017535, No Iterations 2
smoothSolver:  Solving for Uz, Initial residual = 0.001041301996, Final residual = 8.489900064e-05, No Iterations 2
smoothSolver:  Solving for h, Initial residual = 0.001102059566, Final residual = 9.050933718e-05, No Iterations 2
GAMG:  Solving for p_rgh, Initial residual = 0.01782668781, Final residual = 0.0006434618934, No Iterations 2
time step continuity errors : sum local = 0.004199870883, global = -1.300348859e-05, cumulative = 0.02837629765
rho max/min : 1.61575725 1.027666084
smoothSolver:  Solving for epsilon, Initial residual = 0.0003726036192, Final residual = 1.624410955e-05, No Iterations 2
smoothSolver:  Solving for k, Initial residual = 0.0006769270182, Final residual = 4.100176601e-05, No Iterations 2
ExecutionTime = 43246.23 s  ClockTime = 43324 s

Time = 18887

smoothSolver:  Solving for Ux, Initial residual = 0.0006047473189, Final residual = 4.917024084e-05, No Iterations 2
smoothSolver:  Solving for Uy, Initial residual = 0.001440066594, Final residual = 0.0001178240974, No Iterations 2
smoothSolver:  Solving for Uz, Initial residual = 0.001033277701, Final residual = 8.422450783e-05, No Iterations 2
smoothSolver:  Solving for h, Initial residual = 0.001099930259, Final residual = 9.044716316e-05, No Iterations 2
GAMG:  Solving for p_rgh, Initial residual = 0.01778140607, Final residual = 0.0006504819822, No Iterations 2
time step continuity errors : sum local = 0.004246140865, global = 3.962517019e-05, cumulative = 0.02841592282
rho max/min : 1.614670092 1.02762854
smoothSolver:  Solving for epsilon, Initial residual = 0.000369558813, Final residual = 1.612523952e-05, No Iterations 2
smoothSolver:  Solving for k, Initial residual = 0.0006713037785, Final residual = 4.069978604e-05, No Iterations 2
ExecutionTime = 43248.55 s  ClockTime = 43326 s



I wonder if some one can advise me how to tune the solver to get convergence?
Thank you!
Attached Images
File Type: jpg UCFluidSmallGeometry.jpg (43.8 KB, 32 views)
File Type: jpg UCFluidSmallMesh.jpg (96.1 KB, 29 views)
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Old   January 18, 2014, 07:58
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Mostafa Mahmoudi
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hi skuznet,

Perhaps, with assuming your grid is fine enough, your boundary conditions for your turbulent model are not match with your case. they could affect the velocities strongly. I had same problem with my residuals, but for a simpler geometry, when I changed my turbulent BC my model solved.
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Old   February 18, 2014, 17:42
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Cong
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Quote:
Originally Posted by adambarfi View Post
hi skuznet,

Perhaps, with assuming your grid is fine enough, your boundary conditions for your turbulent model are not match with your case. they could affect the velocities strongly. I had same problem with my residuals, but for a simpler geometry, when I changed my turbulent BC my model solved.
Hi, i have similar problems. My pressure residual is between 0.01 - 0.1 and does NOT decrease with more iterations.

How to solve it?

I really appreciate your help.
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Old   February 18, 2014, 18:14
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Sergey
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Can you please give me an advise how do I choose turbulent BC to match model?
Or any reference please,

Thanks!
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Old   February 18, 2014, 23:05
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Dear Cong,
It depends on several parameters, your geometry, mesh, solvers, BCs, etc.
Please post some additional information.

Dear Sergey,
Depending on your geometry and the the nature of flow, you should get some proper papers in the field you are working and surely they have some tips for you. also you can use this cfd-online tool: http://www.cfd-online.com/Tools/turbulence.php
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Old   February 19, 2014, 05:30
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Cong
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Quote:
Originally Posted by adambarfi View Post
Dear Cong,
It depends on several parameters, your geometry, mesh, solvers, BCs, etc.
Please post some additional information.

Dear Sergey,
Depending on your geometry and the the nature of flow, you should get some proper papers in the field you are working and surely they have some tips for you. also you can use this cfd-online tool: http://www.cfd-online.com/Tools/turbulence.php
Hello Mostafa,

thank you for your help.

As a matter of fact, my first case is quite simple. A box with 6 isothermal walls, no inlet or outlet. I chose k-omega SST model and buoyantSimpleFoam. Mesh is refined closed to the wall and also layers are added.
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