[Marie_Dal]

Hello everyone,
I am new to OpenFoam. I am currently running a simulation of an airfoil using SimpleFoam with the turbulence model KomegaSST LM. After just a few iterations (4), the value of bounding omega (max) starts to be very high, which I believe is the reason why a warning appears a couple iterations after:

--> FOAM Warning :
From function Foam::tmp<Foam::DimensionedField<double, Foam::volMesh> > Foam::RASModels::kOmegaSSTLM<BasicMomentumTranspor tModel>::ReThetat0(const Internal&, const Internal&, const Internal&) const [with BasicMomentumTransportModel = Foam::IncompressibleMomentumTransportModel<Foam::k inematicTransportModel>; Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh>::Internal = Foam::DimensionedField<double, Foam::volMesh>]
in file ../momentumTransportModels/lnInclude/kOmegaSSTLM.C at line 300
Number of lambda iterations exceeds maxLambdaIter(10)

Now in my very little experience with this turbulence model, I believe this to be a boundary condition problem. I tried different values for omega, using wall functions for k, omega and nut, and also removing them, but nothing seems to work.

I tried turning my turbulence model back to the K omega SST, and the simulation runs without inconvenience, for which I assume the mesh is not the problem.

This is what an itertion with this warning looks like:

Time = 6

smoothSolver: Solving for Ux, Initial residual = 0.0493299, Final residual = 0.00422165, No Iterations 5
smoothSolver: Solving for Uy, Initial residual = 0.249744, Final residual = 0.0204515, No Iterations 4
GAMG: Solving for p, Initial residual = 0.107384, Final residual = 0.00826549, No Iterations 3
time step continuity errors : sum local = 0.000609625, global = -6.2441e-06, cumulative = -1.32525e-05
--> FOAM Warning :
From function Foam::tmp<Foam::DimensionedField<double, Foam::volMesh> > Foam::RASModels::kOmegaSSTLM<BasicMomentumTranspor tModel>::ReThetat0(const Internal&, const Internal&, const Internal&) const [with BasicMomentumTransportModel = Foam::IncompressibleMomentumTransportModel<Foam::k inematicTransportModel>; Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh>::Internal = Foam::DimensionedField<double, Foam::volMesh>]
in file ../momentumTransportModels/lnInclude/kOmegaSSTLM.C at line 300
Number of lambda iterations exceeds maxLambdaIter(10)
smoothSolver: Solving for ReThetat, Initial residual = 0.0628862, Final residual = 0.00492529, No Iterations 5
smoothSolver: Solving for gammaInt, Initial residual = 0.00826379, Final residual = 0.000491998, No Iterations 4
bounding gammaInt, min: -0.0724182 max: 1.11402 average: 0.963246
smoothSolver: Solving for omega, Initial residual = 0.0155426, Final residual = 0.00154728, No Iterations 6
bounding omega, min: -112.337 max: 2.47547e+10 average: 1.1801e+06
smoothSolver: Solving for k, Initial residual = 0.998501, Final residual = 7.2704e-05, No Iterations 1
ExecutionTime = 6.61 s ClockTime = 7 s



An error finally comes up after 18 iterations, when everything has already diverged:

Time = 18

smoothSolver: Solving for Ux, Initial residual = 0.730684, Final residual = 3.77352e+08, No Iterations 10
smoothSolver: Solving for Uy, Initial residual = 0.658047, Final residual = 3.8716e+08, No Iterations 10
#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::GAMGSolver::scale(Foam::Field<double>&, Foam::Field<double>&, Foam::lduMatrix const&, Foam::FieldField<Foam::Field, double> const&, Foam::UPtrList<Foam::lduInterfaceField const> const&, Foam::Field<double> const&, unsigned char) const at ??:?
#4 Foam::GAMGSolver::Vcycle(Foam::PtrList<Foam::lduMa trix::smoother> const&, Foam::Field<double>&, Foam::Field<double> const&, Foam::Field<double>&, Foam::Field<double>&, Foam::Field<double>&, Foam::Field<double>&, Foam::Field<double>&, Foam::PtrList<Foam::Field<double> >&, Foam::PtrList<Foam::Field<double> >&, unsigned char) const at ??:?
#5 Foam::GAMGSolver::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const at ??:?
#6 Foam::fvMatrix<double>::solveSegregated(Foam::dict ionary const&) at ??:?
#7 Foam::fvMatrix<double>::solve(Foam::dictionary const&) in "/opt/openfoam9/platforms/linux64GccDPInt32Opt/bin/simpleFoam"
#8 Foam::fvMatrix<double>::solve() in "/opt/openfoam9/platforms/linux64GccDPInt32Opt/bin/simpleFoam"
#9 ? in "/opt/openfoam9/platforms/linux64GccDPInt32Opt/bin/simpleFoam"
#10 __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6"
#11 ? in "/opt/openfoam9/platforms/linux64GccDPInt32Opt/bin/simpleFoam"



I have faced very similar problems with other simulations, but changing boundary conditions (usually rising the value for omega) has always seemed to fix them. Yet, no matter what I try with this simulation, I can't seem to fix it.

I very much appreciate anyone's advice. I attach below boundary conditions and gradient schemes.

Thank you. :)

BOUNDARY CONDITIONS:

GammaInt:

internalField uniform 1;
boundaryField
{ inlet { type fixedValue;
value $internalField; }
outlet
{ type zeroGradient; }
walls
{ type zeroGradient; }
airfoil
{ type zeroGradient; }
frontAndBackPlanes
{ type empty; } }


K:
internalField uniform 0.00135;

boundaryField
{ inlet
{ type fixedValue;
value uniform 0.00135; }
outlet
{ type zeroGradient; }
airfoil
{ type fixedValue;
value uniform 1e-6; }
walls
{ type zeroGradient; }
frontAndBackPlanes
{ type empty; }}

nut
internalField uniform 0.0020125;

boundaryField
{ inlet { type freestream;
freestreamValue uniform 0.0020125; }

outlet { type freestream;
freestreamValue uniform 0.0020125; }

airfoil { type nutkWallFunction;
value uniform 0.00000020125; }

walls { type zeroGradient; }

frontAndBackPlanes { type empty; }}


OMEGA:
dimensions [0 0 -1 0 0 0 0];

internalField uniform 2.6708;

boundaryField
{ inlet { type fixedValue;
value $internalField; }

outlet { type zeroGradient; }

airfoil { type omegaWallFunction;
value $internalField; }

walls { type zeroGradient; }

frontAndBackPlanes { type empty; }}



ReThetaT
internalField uniform 1170.563958;
boundaryField
{ inlet { type fixedValue;
value $internalField; }

outlet { type zeroGradient; }

walls { type zeroGradient; }

airfoil { type zeroGradient; }

frontAndBackPlanes { type empty; }}

For U and P I use freeStream and no slip conditions on the airfoil, altough those boundary conditions are vastly tested and I am certain those are not the problem.