# why pisoFoam take such a long time to converge?

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 October 18, 2013, 09:59 #41 Senior Member     Philipp Join Date: Jun 2011 Location: Germany Posts: 1,297 Rep Power: 26 And you don't expect a vortex street? DaSh likes this. __________________ The skeleton ran out of shampoo in the shower.

October 18, 2013, 13:00
#42
Senior Member

izna O'connor
Join Date: Jun 2013
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hello

its still simulating and this si the type of output am receiving at terminall.

Quote:
 Time = 959 --> FOAM Warning : From function gaussConvectionScheme in file finiteVolume/convectionSchemes/gaussConvectionScheme/gaussConvectionScheme.H at line 123 Reading "/home/izna/Desktop/me/system/fvSchemes.divSchemes.default" at line 27 Unbounded 'Gauss' div scheme used in steady-state solver, use 'bounded Gauss' to ensure boundedness. To remove this warning switch off 'boundedGauss' in "/opt/openfoam221/etc/controlDict" smoothSolver: Solving for Ux, Initial residual = 0.000382259389777, Final residual = 3.81330355835e-06, No Iterations 8 smoothSolver: Solving for Uy, Initial residual = 0.000406555532739, Final residual = 3.58434203503e-06, No Iterations 8 GAMG: Solving for p, Initial residual = 0.133891930631, Final residual = 0.000949864543092, No Iterations 3 GAMG: Solving for p, Initial residual = 0.0077554604295, Final residual = 5.79583585482e-05, No Iterations 4 GAMG: Solving for p, Initial residual = 0.00260690611916, Final residual = 2.45334009184e-05, No Iterations 3 time step continuity errors : sum local = 1.47964141313e-08, global = 1.65204514718e-10, cumulative = 3.25524797128e-08 --> FOAM Warning : From function gaussConvectionScheme in file finiteVolume/convectionSchemes/gaussConvectionScheme/gaussConvectionScheme.H at line 123 Reading "/home/izna/Desktop/me/system/fvSchemes.divSchemes.default" at line 27 Unbounded 'Gauss' div scheme used in steady-state solver, use 'bounded Gauss' to ensure boundedness. To remove this warning switch off 'boundedGauss' in "/opt/openfoam221/etc/controlDict" smoothSolver: Solving for epsilon, Initial residual = 0.000171819786028, Final residual = 1.47516065563e-05, No Iterations 4 bounding epsilon, min: 3.49835487563e-16 max: 1 average: 0.00013971873233 --> FOAM Warning : From function gaussConvectionScheme in file finiteVolume/convectionSchemes/gaussConvectionScheme/gaussConvectionScheme.H at line 123 Reading "/home/izna/Desktop/me/system/fvSchemes.divSchemes.default" at line 27 Unbounded 'Gauss' div scheme used in steady-state solver, use 'bounded Gauss' to ensure boundedness. To remove this warning switch off 'boundedGauss' in "/opt/openfoam221/etc/controlDict" smoothSolver: Solving for k, Initial residual = 0.0017257154661, Final residual = 0.000146662614997, No Iterations 4 bounding k, min: 3.91148869528e-16 max: 0.681259530278 average: 0.0479703205957 ExecutionTime = 10639.86 s ClockTime = 10667 s

 October 18, 2013, 13:14 #43 Senior Member   izna O'connor Join Date: Jun 2013 Posts: 143 Rep Power: 12 hi yeah i am expecting a vortex but at the end of the buildings.. and also it shoudl be symmetric.. i mean it should be something which is acceptable according to the flow pattern of wind.. for example i am posting a pic where it was with pisofFoam.. this si the sort of result am expecting..( it has not yet conveged in pisofoam.) in the simpleFoam picture.. its not logical.. way after the shape we observe a high velocity region .. this has no logic. Last edited by izna; October 22, 2013 at 10:45.

October 20, 2013, 14:26
#44
Senior Member

izna O'connor
Join Date: Jun 2013
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Rep Power: 12
Quote:
 Time = 11003 --> FOAM Warning : From function gaussConvectionScheme in file finiteVolume/convectionSchemes/gaussConvectionScheme/gaussConvectionScheme.H at line 123 Reading "/home/izna/Desktop/me/system/fvSchemes.divSchemes.default" at line 27 Unbounded 'Gauss' div scheme used in steady-state solver, use 'bounded Gauss' to ensure boundedness. To remove this warning switch off 'boundedGauss' in "/opt/openfoam221/etc/controlDict" smoothSolver: Solving for Ux, Initial residual = 2.7007949779e-08, Final residual = 2.41921188974e-09, No Iterations 1 smoothSolver: Solving for Uy, Initial residual = 6.15313317584e-09, Final residual = 6.15313317584e-09, No Iterations 0 #0 Foam::error:rintStack(Foam::Ostream&) in "/opt/openfoam221/platforms/linuxGccDPOpt/lib/libOpenFOAM.so" #1 Foam::sigFpe::sigHandler(int) in "/opt/openfoam221/platforms/linuxGccDPOpt/lib/libOpenFOAM.so" #2 Uninterpreted: #3 Foam:ICPreconditioner::calcReciprocalD(Foam::Fie ld&, Foam::lduMatrix const&) in "/opt/openfoam221/platforms/linuxGccDPOpt/lib/libOpenFOAM.so" #4 Foam:ICSmoother:ICSmoother(Foam::word const&, Foam::lduMatrix const&, Foam::FieldField const&, Foam::FieldField const&, Foam::UPtrList const&) in "/opt/openfoam221/platforms/linuxGccDPOpt/lib/libOpenFOAM.so" #5 Foam:ICGaussSeidelSmoother:ICGaussSeidelSmooth er(Foam::word const&, Foam::lduMatrix const&, Foam::FieldField const&, Foam::FieldField const&, Foam::UPtrList const&) in "/opt/openfoam221/platforms/linuxGccDPOpt/lib/libOpenFOAM.so" #6 Foam::lduMatrix::smoother::addsymMatrixConstructor ToTable::New(Foam::w ord const&, Foam::lduMatrix const&, Foam::FieldField const&, Foam::FieldField const&, Foam::UPtrList const&) in "/opt/openfoam221/platforms/linuxGccDPOpt/lib/libOpenFOAM.so" #7 Foam::lduMatrix::smoother::New(Foam::word const&, Foam::lduMatrix const&, Foam::FieldField const&, Foam::FieldField const&, Foam::UPtrList const&, Foam::dictionary const&) in "/opt/openfoam221/platforms/linuxGccDPOpt/lib/libOpenFOAM.so" #8 Foam::GAMGSolver::initVcycle(Foam::PtrList >&, Foam::PtrList >&, Foam::PtrList&) const in "/opt/openfoam221/platforms/linuxGccDPOpt/lib/libOpenFOAM.so" #9 Foam::GAMGSolver::solve(Foam::Field&, Foam::Field const&, unsigned char) const in "/opt/openfoam221/platforms/linuxGccDPOpt/lib/libOpenFOAM.so" #10 Foam::fvMatrix::solveSegregated(Foam::dict ionary const&) in "/opt/openfoam221/platforms/linuxGccDPOpt/lib/libfiniteVolume.so" #11 Foam::fvMatrix::solve(Foam::dictionary const&) in "/opt/openfoam221/platforms/linuxGccDPOpt/bin/simpleFoam" #12 in "/opt/openfoam221/platforms/linuxGccDPOpt/bin/simpleFoam" #13 __libc_start_main in "/lib/i386-linux-gnu/libc.so.6" #14 in "/opt/openfoam221/platforms/linuxGccDPOpt/bin/simpleFoam" Floating point exception (core dumped)
this is the error message posted after 11003 iteration ... till now everuything was fine.. but arriving at this all stop..

 October 21, 2013, 02:46 #45 Senior Member     Philipp Join Date: Jun 2011 Location: Germany Posts: 1,297 Rep Power: 26 This is what hakoon already wrote in this thread: Maybe your flow is not able to converge to a steady state because it is too unstable. Flows over bluff-bodies can sometimes converge with RANS models (steady-state), but that solution doesn't make any sense at all. The vortex street forces the unsteadyness - averaging of this flow is physically nonsense. So it can be, that you really need pisoFoam. But then, you don't have any steady-state solution. __________________ The skeleton ran out of shampoo in the shower.

October 24, 2013, 06:49
#46
Senior Member

T. Chourushi
Join Date: Jul 2009
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Quote:
 Originally Posted by izna this is the error message posted after 11003 iteration ... till now everuything was fine.. but arriving at this all stop.. Advice..
Do the following:

(1) PISO:

use
divSchemes
{
default none;
div(phi,U) Gauss upwind;
div(phi,k) Gauss upwind;
......
}
(2) SIMPLE:

use
divSchemes
{
default none;
div(phi,U) bounded Gauss upwind;
div(phi,k) bounded Gauss upwind;
......
}

 October 24, 2013, 13:43 #47 Senior Member   izna O'connor Join Date: Jun 2013 Posts: 143 Rep Power: 12 hi You mean run bth piso and simple in simpleFoam?

October 25, 2013, 00:04
#48
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T. Chourushi
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Quote:
 Originally Posted by izna hi You mean run bth piso and simple in simpleFoam?
Well,

(1) The key-word: PISO (unsteady-state) refers to the pisoFoam

(2) And, the key-word SIMPLE (steady-state) refers to the simpleFoam.

In my earlier posting.

October 25, 2013, 00:16
#49
Senior Member

izna O'connor
Join Date: Jun 2013
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Quote:
 --> FOAM FATAL IO ERROR: keyword div((nuEff*dev(T(grad(U))))) is undefined in dictionary "/home/izna/Desktop/uomopenFoa/system/fvSchemes.divSchemes" file: /home/izna/Desktop/uomopenFoa/system/fvSchemes.divSchemes from line 27 to line 29. From function dictionary::lookupEntry(const word&, bool, bool) const in file db/dictionary/dictionary.C at line 402. FOAM exiting
error on using with simpleFoam..

Last edited by izna; October 25, 2013 at 03:14.

October 25, 2013, 00:50
#50
Senior Member

T. Chourushi
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Quote:
 Originally Posted by izna error on using with simpleFoam..
The keyword "div((nuEff*dev(T(grad(U)))))" has not been assigned scheme - "bounded Gauss upwind" for the simpleFoam. So, the error msg is displayed. For more information you can refer to the openfoam website.

 October 25, 2013, 02:07 #51 Senior Member   izna O'connor Join Date: Jun 2013 Posts: 143 Rep Power: 12 i have copied and paste your answer!! hence i obtain thsi error..! i though u wanted me to try with only that condition!

October 25, 2013, 02:28
#52
Senior Member

T. Chourushi
Join Date: Jul 2009
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Quote:
 Originally Posted by izna i have copied and paste your answer!! hence i obtain thsi error..! i though u wanted me to try with only that condition!
Oh! I forgot to see the term "nuEff", for this case you go with bounded Gauss linear. Rest all divSchemes as bounded Gauss upwind. Try running with it and check your answer.