[libra]

Hi everyone
I am simulating the water flow in a pipe using LES with OpenFoam version 1.6.
It seems that there is something wrong with "courant number" in my computations. During the computations it gets bigger and bigger and finally the computation stops. The value I should choose for courant number is 5*10^-4 according to the calculations, but I have even chosen a smaller value: 10^-5. I am wondering why this number gets so big?????

[niaz]

Dear libra
it is big problem in openfoam. but it has easy solution
you can limit your courant with "maxCo 0.2;"
it controls your courant and adapt your time steps.

[libra]

Hi Niaz
Thanks for your comment. I limited the Courant number and my computation is running for now. I hope it works.

[libra]

Originally Posted by niaz

Dear libra
it is big problem in openfoam. but it has easy solution
you can limit your courant with "maxCo 0.2;"
it controls your courant and adapt your time steps.

Dear Niaz
I changed my "controlDict" file to the following to limit the courant number:

/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 1.6 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
location "system";
object controlDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

application channelFoam;

startFrom startTime;

startTime 0;

stopAt endTime;

endTime 1;

deltaT 1e-5;

writeControl adjustableRunTime;

writeInterval 100;

purgeWrite 0;

writeFormat ascii;

writePrecision 6;

writeCompression uncompressed;

timeFormat general;

timePrecision 6;

runTimeModifiable yes;

adjustTimeStep yes;

maxCo 0.5;

maxDeltaT 1;

functions
{
fieldAverage1
{
type fieldAverage;
functionObjectLibs ( "libfieldFunctionObjects.so" );
enabled true;
outputControl outputTime;
fields
(
U
{
mean on;
prime2Mean on;
base time;
}

p
{
mean on;
prime2Mean on;
base time;
}
);
}
}


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

But it didn't work and the courant number exceeds 0.5. Do you have any idea about this?
Thanks

[niaz]

Libra
channelFoam cannot control courant number.
you should add setDeltaT.H to your solver.

[niaz]

If you need help just look at pimpleFoam as an example.

[libra]

Thanks Niaz. Problem solved.

[DuarteMagalhaes]

Hi everyone. I'm using icoFoam and i want to control the Courant number. I've tried to insert "maxCo 0.5;" in the controlDict file, but it didn't work. Can anyone help me on this?

[Bernhard]

Originally Posted by DuarteMagalhaes

Hi everyone. I'm using icoFoam and i want to control the Courant number. I've tried to insert "maxCo 0.5;" in the controlDict file, but it didn't work. Can anyone help me on this?

The solution is in this topic. Read carefully!