CFD Online Discussion Forums - why pisoFoam take such a long time to converge?

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- - why pisoFoam take such a long time to converge? (https://www.cfd-online.com/Forums/openfoam-solving/124845-why-pisofoam-take-such-long-time-converge.html)

And you don't expect a vortex street?

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

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.

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::printStack(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::DICPreconditioner::calcReciprocalD(Foam::Fie ld<double>&, Foam::lduMatrix const&) in "/opt/openfoam221/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#4 Foam::DICSmoother::DICSmoother(Foam::word const&, Foam::lduMatrix const&, Foam::FieldField<Foam::Field, double> const&, Foam::FieldField<Foam::Field, double> const&, Foam::UPtrList<Foam::lduInterfaceField const> const&) in "/opt/openfoam221/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#5 Foam::DICGaussSeidelSmoother::DICGaussSeidelSmooth er(Foam::word const&, Foam::lduMatrix const&, Foam::FieldField<Foam::Field, double> const&, Foam::FieldField<Foam::Field, double> const&, Foam::UPtrList<Foam::lduInterfaceField const> const&) in "/opt/openfoam221/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#6 Foam::lduMatrix::smoother::addsymMatrixConstructor ToTable<Foam::DICGaussSeidelSmoother>::New(Foam::w ord const&, Foam::lduMatrix const&, Foam::FieldField<Foam::Field, double> const&, Foam::FieldField<Foam::Field, double> const&, Foam::UPtrList<Foam::lduInterfaceField const> const&) in "/opt/openfoam221/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#7 Foam::lduMatrix::smoother::New(Foam::word const&, Foam::lduMatrix const&, Foam::FieldField<Foam::Field, double> const&, Foam::FieldField<Foam::Field, double> const&, Foam::UPtrList<Foam::lduInterfaceField const> const&, Foam::dictionary const&) in "/opt/openfoam221/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#8 Foam::GAMGSolver::initVcycle(Foam::PtrList<Foam::F ield<double> >&, Foam::PtrList<Foam::Field<double> >&, Foam::PtrList<Foam::lduMatrix::smoother>&) const in "/opt/openfoam221/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#9 Foam::GAMGSolver::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const in "/opt/openfoam221/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#10 Foam::fvMatrix<double>::solveSegregated(Foam::dict ionary const&) in "/opt/openfoam221/platforms/linuxGccDPOpt/lib/libfiniteVolume.so"
#11 Foam::fvMatrix<double>::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..

Advice..

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.

Quote:

Originally Posted by izna (Post 457928)

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;
......
}

Re-Run and check your case.

hi
You mean run bth piso and simple in simpleFoam?

Quote:

Originally Posted by izna (Post 458834)

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.

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..

Quote:

Originally Posted by izna (Post 458891)

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.

i have copied and paste your answer!! hence i obtain thsi error..!
i though u wanted me to try with only that condition!

Quote:

Originally Posted by izna (Post 458903)

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.