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so large Co!! why?

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Old   April 3, 2013, 04:40
Unhappy so large Co!! why?
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chaoqing min
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I am new for the of. why is my Co so large? it is about 10e290. The cells are divieded in x,y,z directions20 20 200); the velocity is z direction, 1m/s; the block is a square of cylinder and r=0.1m, l=1m.

Thanks millions.
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Old   April 3, 2013, 05:12
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Alexey Matveichev
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Can you post case files? Or at least checkMesh output.
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Old   April 3, 2013, 05:33
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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:rintStack(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
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Old   April 3, 2013, 05:38
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Alexey Matveichev
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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 View Post
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:rintStack(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
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Old   April 3, 2013, 05:41
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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
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