[aPostrophic]

Hi,
i have a problem with rhoSimpleFoam(compressible flow over an airfoil). After a few seconds of iteration i get an ERROR because my desity becomes negative. For lower velocities (25 m/s) the solver is working fine.



ILUPBiCG: Solving for Ux, Initial residual = 0.0416817, Final residual = 3.43245e-07, No Iterations 3
DILUPBiCG: Solving for Uy, Initial residual = 0.0547899, Final residual = 7.02575e-07, No Iterations 3
DILUPBiCG: Solving for h, Initial residual = 0.579378, Final residual = 3.346e-06, No Iterations 3
DICPCG: Solving for p, Initial residual = 0.822832, Final residual = 9.23512e-07, No Iterations 217
time step continuity errors : sum local = 0.165649, global = 0.000831612, cumulative = 0.00080585
rho max/min : 1653.12 -529.803
bounding p, min: -2.02969e+08 max: 695295 average: -3.70797e+07
ExecutionTime = 1.62 s ClockTime = 2 s

Time = 22

DILUPBiCG: Solving for Ux, Initial residual = 0.118398, Final residual = 5.61993e-06, No Iterations 3
DILUPBiCG: Solving for Uy, Initial residual = 0.192935, Final residual = 4.42431e-06, No Iterations 3
DILUPBiCG: Solving for h, Initial residual = 0.190434, Final residual = 3.27602e-06, No Iterations 3


Maximum number of iterations exceeded#0 Foam::error:rintStack(Foam::Ostream&) in "/home/++++/OpenFOAM/OpenFOAM-1.6/lib/linux64gcc451DPOpt/libOpenFOAM.so"
#1 Foam::error::abort() at /home/++++/OpenFOAM/OpenFOAM-1.6/src/OpenFOAM/lnInclude/Ostream.H:252
#2 Foam::hPsiThermo<Foam:ureMixture<Foam::constTran sport<Foam::specieThermo<Foam::hConstThermo<Foam:: perfectGas> > > > >::calculate() in "/home/++++/OpenFOAM/OpenFOAM-1.6/lib/linux64gcc451DPOpt/libbasicThermophysicalModels.so"
#3 Foam::hPsiThermo<Foam:ureMixture<Foam::constTran sport<Foam::specieThermo<Foam::hConstThermo<Foam:: perfectGas> > > > >::correct() in "/home/++++/OpenFOAM/OpenFOAM-1.6/lib/linux64gcc451DPOpt/libbasicThermophysicalModels.so"
#4 main at ~/OpenFOAM/++++/applications/myrhoSimpleFoam/hEqn.H:10
#5 __libc_start_main in "/lib64/libc.so.6"
#6 Foam::regIOobject::writeObject(Foam::IOstream::str eamFormat, Foam::IOstream::versionNumber, Foam::IOstream::compressionType) const in "/home/++++OpenFOAM/OpenFOAM-1.6/applications/bin/linux64gcc451DPOpt/myrhoSimpleFoam"


From function specieThermo<thermo>::T(scalar f, scalar T0, scalar (specieThermo<thermo>::*F)(const scalar) const, scalar (specieThermo<thermo>::*dFdT)(const scalar) const) const
in file /home/++++/OpenFOAM/OpenFOAM-1.6/src/thermophysicalModels/specie/lnInclude/specieThermoI.H at line 68.

FOAM aborting





Here are my boundary conditions:

FoamFile
{
version 2.0;
format ascii;
class volScalarField;
object p;
}

dimensions [1 -1 -2 0 0 0 0];

internalField uniform 100000;

boundaryField
{
farfield1
{
type zeroGradient;
}

farfield2
{
type zeroGradient;
}

farfield3
{
type fixedValue;
value $internalField;
}

airfoil
{
type zeroGradient;
}

frontAndBackPlanes
{
type empty;
}
}

// ************************************************** *********************** //


FoamFile
{
version 2.0;
format ascii;
class volScalarField;
object T;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions [0 0 0 1 0 0 0];

internalField uniform 300;




boundaryField
{
farfield1
{
type zeroGradient;
}

farfield2
{
type zeroGradient;
}


farfield3
{
type fixedValue;
value $internalField;

}

airfoil
{
type zeroGradient;
}

frontAndBackPlanes
{
type empty;
}
}


FoamFile
{
version 2.0;
format ascii;
class volVectorField;
object U;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions [0 1 -1 0 0 0 0];

internalField uniform (104 2 0);

boundaryField
{
farfield1
{
type freestream;
value $internalField;

farfield2
{
type freestream;
value $internalField;
}

farfield3
{
type freestream;
value $internalField;
}

airfoil
{
type zeroGradient;
}

frontAndBackPlanes
{
type empty;
}
}

I have switched off the Turbulence model and I use

thermoType hPsiThermo<pureMixture<constTransport<specieThermo <hConstThermo<perfectGas>>>>>;

mixture air 1 28.9 1007 0 1.84e-05 0.7;

Does anybody know what i can do?

[alberto]

I would:

- check relaxation factors
- check the mesh
- try with first-order upwind if you use second order schemes

Best,