CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > OpenFOAM Running, Solving & CFD

fvSchemes, Fina residual tolerance not working

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Display Modes
Old   March 17, 2012, 10:55
Default fvSchemes, Fina residual tolerance not working
  #1
Senior Member
 
Attesz's Avatar
 
Attesz
Join Date: Mar 2009
Posts: 355
Rep Power: 8
Attesz is an unknown quantity at this point
Hi all,

if I set the final residual tolerances, finally the solver doesn't reach the prescribed level. However, if I adjust the tolerance/reltol in the simple U/p etc. it can reach whatever I want. Is it a bug maybe?

Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.1.x                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      fvSolution;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

solvers
{
    pcorr
    {
        solver          GAMG;
        tolerance       1e-2;
        relTol          0;
        smoother        DICGaussSeidel;
        cacheAgglomeration true;
        nCellsInCoarsestLevel 10000;
        agglomerator    faceAreaPair;
        mergeLevels     1;
        maxIter         10;
    }

    p
    {
        $pcorr;
        tolerance       1e-5;
        relTol          0.01;
    }

    pFinal
    {
        $p;
        tolerance       1e-8;
        relTol          0;
    }

    
//parameters for k-omega model
  
    U
    {
        solver          GAMG;
        smoother        DILUGaussSeidel;
    nPreSweeps       0;
        nPostSweeps      2;
        tolerance        1e-4;
        relTol           0;
        cacheAgglomeration true;
        nCellsInCoarsestLevel 10000;
        agglomerator    faceAreaPair;
        mergeLevels     1;
        maxIter         5;
    }

    k
    {
        solver          GAMG;
        smoother        DILUGaussSeidel;
    nPreSweeps       0;
        nPostSweeps      2;
        tolerance        1e-4;
        relTol           0;
        cacheAgglomeration true;
        nCellsInCoarsestLevel 10000;
        agglomerator    faceAreaPair;
        mergeLevels     1;
        maxIter         5;
    }

    omega
    {
        solver          GAMG;
        smoother        DILUGaussSeidel;
    nPreSweeps       0;
        nPostSweeps      2;
        tolerance        1e-4;
        relTol           0;
        cacheAgglomeration true;
        nCellsInCoarsestLevel 10000;
        agglomerator    faceAreaPair;
        mergeLevels     1;
        maxIter         5;
    }
      
    "(U|k|omega)Final"
    {
        solver          PBiCG;
        preconditioner  DILU;
        tolerance       1e-8;
        relTol          0;
    }

}


SIMPLE
{
    nNonOrthogonalCorrectors 5;        //because the mesh is highly not orthogonal. maximum 20, 0 is cartesian hexahedral!
    pRefCell        0;
    pRefValue       0;
    residualControl
    {
        p               1e-4;
        U               1e-4;
        "(k|epsilon|omega)" 1e-4;
    }

}

potentialFlow
{
nNonOrthogonalCorrectors 10;
}

relaxationFactors
{
    fields
    {
        p               0.3;
    }
    equations
    {
        U   0.7;
    k   0.5;
    omega   0.5;
    }
}



// ************************************************************************* //
__________________
CFD= Cleverly Formatted Data
Attesz is offline   Reply With Quote

Old   March 17, 2012, 17:26
Default
  #2
Senior Member
 
David Gaden
Join Date: Apr 2009
Location: Winnipeg, Canada
Posts: 397
Rep Power: 12
marupio is on a distinguished road
Try prescribing something nonesensical in pFinal to see if it's actually even reading it. e.g. tolerance banana;
__________________
~~~
Follow me on twitter @DavidGaden
marupio is offline   Reply With Quote

Old   March 18, 2012, 21:21
Default
  #3
Senior Member
 
Alberto Passalacqua
Join Date: Mar 2009
Location: Ames, Iowa, United States
Posts: 1,894
Rep Power: 26
alberto will become famous soon enoughalberto will become famous soon enough
I see where your confusion can come from. The SIMPLE algorithm does not have any "final" iteration, so the pFinal entry won't be read. The "Final" entries are only used in solvers based on the PIMPLE algorithm, where indeed each integration (time or pseudo-time) step has more than one iteration. In short, the linear solver will give you the final residual you require in "p".

Also, please note that if tolerance is too small, the linear solver will stop at 1000 iterations by default (you can change this value). If you set a high tolerance (say 1.0e-2), the solver will stop at the first iteration below that value, so it would not surprise me if that would be smaller (say something like 0.004).

P.S. I am not so sure it's convenient to use GAMG on anything but p. For steady-state solutions, smoothSolver seems to work better for me.

Best,
__________________
Alberto Passalacqua

GeekoCFD - A free distribution based on openSUSE 64 bit with CFD tools, including OpenFOAM. Available as live DVD/USB, hard drive image and virtual image.
OpenQBMM - An open-source implementation of quadrature-based moment methods

Last edited by alberto; March 18, 2012 at 21:33. Reason: Added comment
alberto is offline   Reply With Quote

Old   March 20, 2012, 04:26
Default
  #4
Senior Member
 
Attesz's Avatar
 
Attesz
Join Date: Mar 2009
Posts: 355
Rep Power: 8
Attesz is an unknown quantity at this point
Alberto, thanks for your comments. Indeed, I didn't see any pFinal nor GAMG for U in tutorial MRFSimpleFoam cases and on the Wiki.

Have a nice day,
Attila
__________________
CFD= Cleverly Formatted Data
Attesz is offline   Reply With Quote

Reply

Thread Tools
Display Modes

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 Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
How to write k and epsilon before the abnormal end xiuying OpenFOAM Running, Solving & CFD 8 August 27, 2013 15:33
High Courant Number @ icoFoam Artex85 OpenFOAM Running, Solving & CFD 9 January 3, 2012 09:06
Orifice Plate with a fully developed flow - Problems with convergence jonmec OpenFOAM Running, Solving & CFD 3 July 28, 2011 05:24
Extrusion with OpenFoam problem No. Iterations 0 Lord Kelvin OpenFOAM 6 April 12, 2011 11:24
Differences between serial and parallel runs carsten OpenFOAM Bugs 11 September 12, 2008 11:16


All times are GMT -4. The time now is 14:13.