high Courant number
 

Hi dear Foamers
I faced to the problem of high Courant number in IcoFoam solver and I need your emergent helps.
what lines should I add to my source code?
where should I put these lines?





/*---------------------------------------------------------------------------*\
========= |
\\ / F ield | OpenFOAM: The Open Source CFD Toolbox
\\ / O peration |
\\ / A nd | Copyright (C) 2011-2012 OpenFOAM Foundation
\\/ M anipulation |
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Application
icoFoam

Description
Transient solver for incompressible, laminar flow of Newtonian fluids.

\*---------------------------------------------------------------------------*/

#include "fvCFD.H"

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

int main(int argc, char *argv[])
{
#include "setRootCase.H"

#include "createTime.H"
#include "createMesh.H"
#include "createFields.H"
#include "initContinuityErrs.H"

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

Info<< "\nStarting time loop\n" << endl;

while (runTime.loop())
{
Info<< "Time = " << runTime.timeName() << nl << endl;

#include "readPISOControls.H"
#include "CourantNo.H"

fvVectorMatrix UEqn
(
fvm::ddt(U)
+ fvm::div(phi, U)
- fvm::laplacian(nu, U)
);

solve(UEqn == -fvc::grad(p));

// --- PISO loop

for (int corr=0; corr<nCorr; corr++)
{
volScalarField rAU(1.0/UEqn.A());

volVectorField HbyA("HbyA", U);
HbyA = rAU*UEqn.H();
surfaceScalarField phiHbyA
(
"phiHbyA",
(fvc::interpolate(HbyA) & mesh.Sf())
+ fvc::ddtPhiCorr(rAU, U, phi)
);

adjustPhi(phiHbyA, U, p);

for (int nonOrth=0; nonOrth<=nNonOrthCorr; nonOrth++)
{
fvScalarMatrix pEqn
(
fvm::laplacian(rAU, p) == fvc::div(phiHbyA)
);

pEqn.setReference(pRefCell, pRefValue);
pEqn.solve();

if (nonOrth == nNonOrthCorr)
{
phi = phiHbyA - pEqn.flux();
}
}

#include "continuityErrs.H"

U = HbyA - rAU*fvc::grad(p);
U.correctBoundaryConditions();
}

fvScalarMatrix TEqn
(
fvm::ddt(T)
+ fvm::div(phi, T)
- fvm::laplacian(alpha, T)
);

TEqn.solve();

runTime.write();

Info<< "ExecutionTime = " << runTime.elapsedCpuTime() << " s"
<< " ClockTime = " << runTime.elapsedClockTime() << " s"
<< nl << endl;
}

Info<< "End\n" << endl;

return 0;
}


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


I look forward to your helps.
thanks.

Hi,

courant number blowing up is often due to stability issues. could you give more details about your case viz. mesh, b.c's, solvers and schemes that you have used ?
Also, post error you are getting when you run icoFoam.

achyutan