[geth03]

ok lets try this then:
1. start the simulation with superslow velocity, maybe only 1/10 or 1/20 or 1/50 or even 1/100. you get my point.
2. also change the viscosity of the fluid to a higher value, btw what is your viscosity like?

[efsolat]

Originally Posted by geth03

ok lets try this then:
1. start the simulation with superslow velocity, maybe only 1/10 or 1/20 or 1/50 or even 1/100. you get my point.
2. also change the viscosity of the fluid to a higher value, btw what is your viscosity like?

Thank you geth03 for putting your time.
In my simulation, the flow is very slow for which the Reynolds number is of the order of e-04

transportModel Newtonian;
   nu     1e-6;
   rho    1000;

and i decreased the velocity 2 order of magnitude as you suggested. the same error occurred as below

time step continuity errors : sum local = 1.54089e+65, global = 5.03892e+64, cumulative = 5.03892e+64
PIMPLE: iteration 5
#0  Foam::error::printStack(Foam::Ostream&) at ??:?
#1  Foam::sigFpe::sigHandler(int) at ??:?
#2  ? in /lib/x86_64-linux-gnu/libc.so.6
#3  void Foam::lduInterfaceField::addToInternalField<double>(Foam::Field<double>&, bool, Foam::Field<double> const&, Foam::Field<double> const&) const at ??:?
#4  Foam::cyclicFvPatchField<Foam::Vector<double> >::updateInterfaceMatrix(Foam::Field<double>&, bool, Foam::Field<double> const&, Foam::Field<double> const&, unsigned char, Foam::UPstream::commsTypes) const at ??:?
#5  Foam::lduMatrix::updateMatrixInterfaces(bool, Foam::FieldField<Foam::Field, double> const&, Foam::UPtrList<Foam::lduInterfaceField const> const&, Foam::Field<double> const&, Foam::Field<double>&, unsigned char) const at ??:?
#6  Foam::symGaussSeidelSmoother::smooth(Foam::word const&, Foam::Field<double>&, Foam::lduMatrix const&, Foam::Field<double> const&, Foam::FieldField<Foam::Field, double> const&, Foam::UPtrList<Foam::lduInterfaceField const> const&, unsigned char, int) at ??:?
#7  Foam::symGaussSeidelSmoother::smooth(Foam::Field<double>&, Foam::Field<double> const&, unsigned char, int) const at ??:?
#8  Foam::smoothSolver::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const at ??:?
#9  Foam::fvMatrix<Foam::Vector<double> >::solveSegregated(Foam::dictionary const&) at ??:?
#10  Foam::fvMatrix<Foam::Vector<double> >::solveSegregatedOrCoupled(Foam::dictionary const&) at ??:?
#11  Foam::fvMesh::solve(Foam::fvMatrix<Foam::Vector<double> >&, Foam::dictionary const&) const at ??:?
#12  ? in ~/OpenFOAM/OpenFOAM-v1912/platforms/linux64GccDPInt32Opt/bin/pimpleFoam
#13  __libc_start_main in /lib/x86_64-linux-gnu/libc.so.6
#14  ? in ~/OpenFOAM/OpenFOAM-v1912/platforms/linux64GccDPInt32Opt/bin/pimpleFoam

\
I am not familiar with C++ but from the bold keywords i guessed that the problem might be due to baffles i created as the interface between the fluid media and the porous one.

in short, i made the geometry with blockmMesh and then separated some cell zones and defined baffles between them. i set the BCs of the baffles as cyclic (for U) and porousBafflePressure (for p). To examine my guess about the problem i changed the pressure BC to cyclic and executed the application. it progressed without the above error but the time step continuity errors exploded after 11 iterations (time step continuity errors : sum local = 2.00222e+09, global = -6.33137e+07, cumulative = -6.33139e+07
PIMPLE: iteration 12
) and i stopped it.
Since then i have googled and tried other BCs for baffles but no one seems useful and it doesn't run with the following error.

Starting time loop

Courant Number mean: 8.40068e-07 max: 0.036
Time = 0.005

PIMPLE: iteration 1
smoothSolver:  Solving for Ux, Initial residual = 3.35635e-07, Final residual = 3.35635e-07, No Iterations 0
smoothSolver:  Solving for Uy, Initial residual = 0.0226208, Final residual = 3.06616e-18, No Iterations 3
smoothSolver:  Solving for Uz, Initial residual = 0.000112152, Final residual = 1.16803e-22, No Iterations 3
#0  Foam::error::printStack(Foam::Ostream&) at ??:?
#1  Foam::sigFpe::sigHandler(int) at ??:?
#2  ? in /lib/x86_64-linux-gnu/libc.so.6
#3  Foam::DICPreconditioner::calcReciprocalD(Foam::Field<double>&, Foam::lduMatrix const&) at ??:?
#4  Foam::DICPreconditioner::DICPreconditioner(Foam::lduMatrix::solver const&, Foam::dictionary const&) at ??:?
#5  Foam::lduMatrix::preconditioner::addsymMatrixConstructorToTable<Foam::DICPreconditioner>::New(Foam::lduMatrix::solver const&, Foam::dictionary const&) at ??:?
#6  Foam::lduMatrix::preconditioner::New(Foam::lduMatrix::solver const&, Foam::dictionary const&) at ??:?
#7  Foam::PBiCGStab::scalarSolve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const at ??:?
#8  Foam::PBiCGStab::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const at ??:?
#9  Foam::fvMatrix<double>::solveSegregated(Foam::dictionary const&) at ??:?
#10  Foam::fvMatrix<double>::solveSegregatedOrCoupled(Foam::dictionary const&) at ??:?
#11  Foam::fvMesh::solve(Foam::fvMatrix<double>&, Foam::dictionary const&) const at ??:?
#12  ? in ~/OpenFOAM/OpenFOAM-v1912/platforms/linux64GccDPInt32Opt/bin/pimpleFoam
#13  __libc_start_main in /lib/x86_64-linux-gnu/libc.so.6
#14  ? in ~/OpenFOAM/OpenFOAM-v1912/platforms/linux64GccDPInt32Opt/bin/pimpleFoam

I know that the way i am trying to solve the problem seems as trial and error it is less than 6 months i have started learning OF


Any suggestion and/or advice would be helpful.
Regards

[HappyS5]

If not, what is your write interval set at? It should be a time value when using adjustibleRuneTime and MaxCo. It will not likely help you converge, though. Please post your file.

[efsolat]

This is the controlDict file

application     pimpleFoam;

startFrom       startTime;//latestTime;//

startTime       0;

stopAt          endTime;

endTime         5;

deltaT          0.005;

writeControl    timeStep;

writeInterval   4;

purgeWrite      0;

writeFormat      ascii;

writePrecision  6;

writeCompression off;

timeFormat      general;

timePrecision   6;

runTimeModifiable true;

adjustTimeStep false;//true;
maxCo           1;
maxAlphaCo      0.7;
maxDeltaT       0.05;

Regards

[HappyS5]

Originally Posted by efsolat

This is the controlDict file

application     pimpleFoam;

startFrom       startTime;//latestTime;//

startTime       0;

stopAt          endTime;

endTime         5;

deltaT          0.005;

writeControl    timeStep;

writeInterval   4;

purgeWrite      0;

writeFormat      ascii;

writePrecision  6;

writeCompression off;

timeFormat      general;

timePrecision   6;

runTimeModifiable true;

adjustTimeStep false;//true;
maxCo           1;
maxAlphaCo      0.7;
maxDeltaT       0.05;

Regards

The writecontrol should be <adjustibleRuntime>, the write interval should be at least 5 saves of your actual time step.

I believe your deltaT is causing your divergence. It is not being adjusted to control your MaxCo.

[geth03]

good point from HappyS5,

when starting a simulation, and especially complex simulations, it is quite likely that your initial conditions are not well set.
when starting a simulation, you should therefore set your initial deltaT to very low numbers, lets say 0.0000005 or so, and adjust it via the maxCo utility. maxCo also won't change deltaT rapidly, rather smoothly, so it will be difficult that your simulation diverges just because of deltaT adjustment.

[efsolat]

In spite of putting much time on the issue but still struggling with the same problem and no progress achieved.


Any help would be of great appreciation.