CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   OpenFOAM Running, Solving & CFD (http://www.cfd-online.com/Forums/openfoam-solving/)
-   -   so large Co!! why? (http://www.cfd-online.com/Forums/openfoam-solving/115608-so-large-co-why.html)

nennbs April 3, 2013 04:40

so large Co!! why?
 
I am new for the of. why is my Co so large? it is about 10e290. The cells are divieded in x,y,z directions:(20 20 200); the velocity is z direction, 1m/s; the block is a square of cylinder and r=0.1m, l=1m.

Thanks millions.

alexeym April 3, 2013 05:12

Can you post case files? Or at least checkMesh output.

nennbs April 3, 2013 05:33

thank you at first.

the output as follows:
Create time

Create mesh for time = 0

Reading transportProperties

Reading field p

Reading field U

Reading/calculating face flux field phi


Starting time loop

Time = 0.0005

Courant Number mean: 4.9449e+289 max: 9.70882e+289
#0 Foam::error::printStack(Foam::Ostream&) in "/home/ifas/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#1 Foam::sigFpe::sigHandler(int) in "/home/ifas/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#2 in "/lib64/libc.so.6"
#3 void Foam::fvc::surfaceIntegrate<Foam::Vector<double> >(Foam::Field<Foam::Vector<double> >&, Foam::GeometricField<Foam::Vector<double>, Foam::fvsPatchField, Foam::surfaceMesh> const&) in "/home/ifas/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/lib/libfiniteVolume.so"
#4 Foam::tmp<Foam::GeometricField<Foam::Vector<double >, Foam::fvPatchField, Foam::volMesh> > Foam::fvc::surfaceIntegrate<Foam::Vector<double> >(Foam::GeometricField<Foam::Vector<double>, Foam::fvsPatchField, Foam::surfaceMesh> const&) in "/home/ifas/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/lib/libfiniteVolume.so"
#5 Foam::tmp<Foam::GeometricField<Foam::Vector<double >, Foam::fvPatchField, Foam::volMesh> > Foam::fvc::div<Foam::Vector<double> >(Foam::GeometricField<Foam::Vector<double>, Foam::fvsPatchField, Foam::surfaceMesh> const&) in "/home/ifas/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/lib/libfiniteVolume.so"
#6 Foam::tmp<Foam::GeometricField<Foam::Vector<double >, Foam::fvPatchField, Foam::volMesh> > Foam::fvc::div<Foam::Vector<double> >(Foam::tmp<Foam::GeometricField<Foam::Vector<doub le>, Foam::fvsPatchField, Foam::surfaceMesh> > const&) in "/home/ifas/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/lib/libfiniteVolume.so"
#7 Foam::fv::gaussLaplacianScheme<Foam::Vector<double >, double>::fvmLaplacian(Foam::GeometricField<double, Foam::fvsPatchField, Foam::surfaceMesh> const&, Foam::GeometricField<Foam::Vector<double>, Foam::fvPatchField, Foam::volMesh> const&) in "/home/ifas/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/lib/libfiniteVolume.so"
#8
in "/home/ifas/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/bin/icoFoam"
#9
in "/home/ifas/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/bin/icoFoam"
#10
in "/home/ifas/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/bin/icoFoam"
#11
in "/home/ifas/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/bin/icoFoam"
#12 __libc_start_main in "/lib64/libc.so.6"
#13
at /home/abuild/rpmbuild/BUILD/glibc-2.15/csu/../sysdeps/x86_64/elf/start.S:116
Gleitkomma-Ausnahme

alexeym April 3, 2013 05:38

Maybe I was not clear enough but can you post case files? (0, constant, system folders). Also you can fun checkMesh utility and post output here.

Though it seems to be empty boundary condition somewhere.

Quote:

Originally Posted by nennbs (Post 418032)
thank you at first.

the output as follows:
Create time

Create mesh for time = 0

Reading transportProperties

Reading field p

Reading field U

Reading/calculating face flux field phi


Starting time loop

Time = 0.0005

Courant Number mean: 4.9449e+289 max: 9.70882e+289
#0 Foam::error::printStack(Foam::Ostream&) in "/home/ifas/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#1 Foam::sigFpe::sigHandler(int) in "/home/ifas/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#2 in "/lib64/libc.so.6"
#3 void Foam::fvc::surfaceIntegrate<Foam::Vector<double> >(Foam::Field<Foam::Vector<double> >&, Foam::GeometricField<Foam::Vector<double>, Foam::fvsPatchField, Foam::surfaceMesh> const&) in "/home/ifas/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/lib/libfiniteVolume.so"
#4 Foam::tmp<Foam::GeometricField<Foam::Vector<double >, Foam::fvPatchField, Foam::volMesh> > Foam::fvc::surfaceIntegrate<Foam::Vector<double> >(Foam::GeometricField<Foam::Vector<double>, Foam::fvsPatchField, Foam::surfaceMesh> const&) in "/home/ifas/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/lib/libfiniteVolume.so"
#5 Foam::tmp<Foam::GeometricField<Foam::Vector<double >, Foam::fvPatchField, Foam::volMesh> > Foam::fvc::div<Foam::Vector<double> >(Foam::GeometricField<Foam::Vector<double>, Foam::fvsPatchField, Foam::surfaceMesh> const&) in "/home/ifas/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/lib/libfiniteVolume.so"
#6 Foam::tmp<Foam::GeometricField<Foam::Vector<double >, Foam::fvPatchField, Foam::volMesh> > Foam::fvc::div<Foam::Vector<double> >(Foam::tmp<Foam::GeometricField<Foam::Vector<doub le>, Foam::fvsPatchField, Foam::surfaceMesh> > const&) in "/home/ifas/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/lib/libfiniteVolume.so"
#7 Foam::fv::gaussLaplacianScheme<Foam::Vector<double >, double>::fvmLaplacian(Foam::GeometricField<double, Foam::fvsPatchField, Foam::surfaceMesh> const&, Foam::GeometricField<Foam::Vector<double>, Foam::fvPatchField, Foam::volMesh> const&) in "/home/ifas/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/lib/libfiniteVolume.so"
#8
in "/home/ifas/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/bin/icoFoam"
#9
in "/home/ifas/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/bin/icoFoam"
#10
in "/home/ifas/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/bin/icoFoam"
#11
in "/home/ifas/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/bin/icoFoam"
#12 __libc_start_main in "/lib64/libc.so.6"
#13
at /home/abuild/rpmbuild/BUILD/glibc-2.15/csu/../sysdeps/x86_64/elf/start.S:116
Gleitkomma-Ausnahme


colinB April 3, 2013 05:41

Be careful spoiler is following:

the courant number is defined as follows:

Co = (u * deltaT) / deltaX

with u being the velocity
delta T the time step
and delta X the cell size

Assuming you have a not moving/deforming mesh
deltaX is constant
Assuming further you turned off adjustableTimeStep,
deltaT is constant as well

Now using some mathematics:
To blow up your courant number your speed has to go up

And this is usually due to bad boundary conditions, bad meshing
wrong physical setting, you may choose

I hope I could contribute
regards


All times are GMT -4. The time now is 02:59.