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-   -   How to setup cyclic BCs in simpleFOAM (http://www.cfd-online.com/Forums/openfoam-solving/68781-how-setup-cyclic-bcs-simplefoam.html)

hhuang84 October 1, 2009 13:43

How to setup cyclic BCs in simpleFOAM
 
I am trying to simulate fully developed turbulent flow in a square duct with cyclic BC in simpleFoam with K-Epsilon model. The mesh was generated in pointwise, with cyclic BCs automatically specified. here attach my setup files, but it fail to get a converged solution. Any hits? Thanks in advance.
0/U &p
dimensions [0 1 -1 0 0 0 0];

internalField uniform (0.329 0 0);

boundaryField
{
Cyclic
{
type cyclic;
value uniform (0.329 0 0);
}

Wall
{
type fixedValue;
value uniform (0 0 0);
}

}

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

internalField uniform 0;

boundaryField
{
Cyclic
{
type cyclic;
}

Wall
{
type zeroGradient;
}


}


and I also set Ubar in constant/transportProperties
Ubar Ubar [ 0 1 -1 0 0 0 0 ] (0.329 0 0 );
transportModel Newtonian;

nu nu [ 0 2 -1 0 0 0 0 ] 1.003e-06;
in system/fvSchemes I set
SIMPLE
{

nNonOrthogonalCorrectors 0;
pRefCell 0;
pRefValue 0;
}

I has been trying for days, but got no good results, even if I turned off turbulence. the maximum stream velocity from simpleFoam is 0.329, so the mass is not conserved.

lakeat October 7, 2009 10:38

How about this,
Code:

Cyclic
{
type cyclic;
}

and why did you use simplefoam to simulate a fully developed turbulence???

hhuang84 October 7, 2009 14:51

Any other solvers that can implement the periodic boundary conditions?

santos October 7, 2009 18:48

Have you looked into channelFoam? It can handle cyclics, while simpleFoam doesnt by default (I think).

Regards,
Jose Santos

hhuang84 October 7, 2009 19:51

However, if I just wanna run a laminar or RANS , what solver can I chose?

lakeat October 7, 2009 22:47

Try pisoFoam.

santos October 8, 2009 10:08

For laminar, change LESModel in channelFoam to laminar. For RANS I guess you need to make your own solver, combining eg pisoFoam (as suggested above) and channelFoam.

Regards,
Jose Santos

ouafa October 14, 2009 10:41

hi everybody,

i try to run the biperiodic tutorial channelOoddles initially proposed in LES, with the solver simpleFoam for steady RANS using the K-omega SST model and taking the same parameters Ubar and nu.

so i add the term gradP like in the channelOoddles solver in the Ueqn but the result was a laminar regime even after long time simulations. k and omega are not zero. can someone help me please, here after my proposed:

fvVectorMatrix UEqn
(
fvm::div(phi, U)
+ turbulence->divDevReff(U)
==
flowDirection*gradP

);


UEqn.relax();

eqnResidual = solve
(
UEqn == -fvc::grad(p)
).initialResidual();


maxResidual = max(eqnResidual, maxResidual);

-----------------------------------------------------------------------------

p.boundaryField().updateCoeffs();

volScalarField AU =UEqn.A();
volScalarField rUA = 1.0/UEqn.A();

U = UEqn.H()/AU;


phi = fvc::interpolate(U) & mesh.Sf();
adjustPhi(phi, U, p);


// Non-orthogonal pressure corrector loop
for (int nonOrth=0; nonOrth<=nNonOrthCorr; nonOrth++)
{
fvScalarMatrix pEqn
(
fvm::laplacian(1.0/AU, p) == fvc::div(phi)
);


pEqn.setReference(pRefCell, pRefValue);
// retain the residual from the first iteration
if (nonOrth == 0)
{
eqnResidual = pEqn.solve().initialResidual();
maxResidual = max(eqnResidual, maxResidual);
}
else
{
pEqn.solve();
}


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


# include "continuityErrs.H"

// Explicitly relax pressure for momentum corrector
p.relax();


// Momentum corrector
U -= fvc::grad(p)/AU;
U.correctBoundaryConditions();



// Correct driving force for a constant mass flow rate

// Extract the velocity in the flow direction
dimensionedScalar magUbarStar =
(flowDirection & U)().weightedAverage(mesh.V());


// Calculate the pressure gradient increment needed to
// adjust the average flow-rate to the correct value
dimensionedScalar gragPplus =
(magUbar - magUbarStar)/rUA.weightedAverage(mesh.V());


U += flowDirection*rUA*gragPplus;

gradP += gragPplus;

Info<< "Uncorrected Ubar = " << magUbarStar.value() << tab
<< "pressure gradient = " << gradP.value() << endl;

chegdan August 31, 2011 17:25

channel flow with simpleFoam aka simpleChannelFoam
 
This is an old thread, but its close to what I would like to discuss. I have made some changes to simpleFoam using channelFoam as a guide to model steady-state channel flow using RANS. I noticed this thread that was left hanging....has anyone managed to get periodic boundary conditions in simpleFoam to work WITHOUT direct mapped patches? Ubar and gradP diverge after a few hundred iterations. Thoughts? Below is my code so far.

Dan

Code:


/*---------------------------------------------------------------------------*\
  =========                |
  \\      /  F ield        | OpenFOAM: The Open Source CFD Toolbox
  \\    /  O peration    |
    \\  /    A nd          | Copyright held by original author
    \\/    M anipulation  |
-------------------------------------------------------------------------------
License
    This file is part of OpenFOAM.

    OpenFOAM is free software; you can redistribute it and/or modify it
    under the terms of the GNU General Public License as published by the
    Free Software Foundation; either version 2 of the License, or (at your
    option) any later version.

    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
    for more details.

    You should have received a copy of the GNU General Public License
    along with OpenFOAM; if not, write to the Free Software Foundation,
    Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA

Application
    simpleChannelFoam

Description
    Steady-state solver for incompressible, laminar or turbulent flow with
    periodic boundary conditions

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

#include "fvCFD.H"
#include "singlePhaseTransportModel.H"
#include "IFstream.H"  //added
#include "OFstream.H"  //added
#include "RASModel.H"

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

int main(int argc, char *argv[])
{
#  include "setRootCase.H"
#  include "createTime.H"
#  include "createMesh.H"
#  include "readTransportProperties.H" //added from channelFoam
#  include "createFields.H"
#  include "initContinuityErrs.H"
#  include "createGradP.H" //added from channelFoam

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

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

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

#      include "readSIMPLEControls.H"
#      include "initConvergenceCheck.H"

        p.storePrevIter();

        // Pressure-velocity SIMPLE corrector
       
        turbulence->correct();//moved here

//solve the U-equation

            tmp<fvVectorMatrix> UEqn
            (
                fvm::div(phi, U)
              + turbulence->divDevReff(U)
              ==
                flowDirection*gradP
            );
       
            UEqn().relax();
       
            eqnResidual = solve
            (
                UEqn() == -fvc::grad(p)
            ).initialResidual();
       
            maxResidual = max(eqnResidual, maxResidual);

//end solving the U-equation
//solve the p-equation with SIMPLE Algorithm
            p.boundaryField().updateCoeffs();

            volScalarField rUA = 1.0/UEqn().A();//added
            U = rUA*UEqn().H();
            UEqn.clear();
            phi = fvc::interpolate(U) & mesh.Sf();
            adjustPhi(phi, U, p);

            // Non-orthogonal pressure corrector loop
            for (int nonOrth=0; nonOrth<=nNonOrthCorr; nonOrth++)
            {
                fvScalarMatrix pEqn
                (
                    fvm::laplacian(rUA, p) == fvc::div(phi)
                );

                pEqn.setReference(pRefCell, pRefValue);

                // Retain the residual from the first iteration
                if (nonOrth == 0)
                {
                    eqnResidual = pEqn.solve().initialResidual();
                    maxResidual = max(eqnResidual, maxResidual);
                }
                else
                {
                    pEqn.solve();
                }

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

        #  include "continuityErrs.H"

            // Explicitly relax pressure for momentum corrector
            p.relax();

            // Momentum corrector
            U -= rUA*fvc::grad(p);
            U.correctBoundaryConditions();

//end solve the p-equation with SIMPLE Algorithm

        // Correct driving force for a constant mass flow rate

        // Extract the velocity in the flow direction
        dimensionedScalar magUbarStar =
            (flowDirection & U)().weightedAverage(mesh.V());

        // Calculate the pressure gradient increment needed to
        // adjust the average flow-rate to the correct value
        dimensionedScalar gragPplus =
            (magUbar - magUbarStar)/rUA.weightedAverage(mesh.V());

        U += flowDirection*rUA*gragPplus;

        gradP += gragPplus;

        //- Solve the turbulence equations and correct the turbulence viscosity after U has been updated
        //turbulence->correct();

        Info<< "Uncorrected Ubar = " << magUbarStar.value() << tab
            << "pressure gradient = " << gradP.value() << endl;

        runTime.write();

        #include "writeGradP.H"        //added from channelFoam

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

#      include "convergenceCheck.H"
    }

    Info<< "End\n" << endl;

    return 0;
}


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


tom ato July 11, 2012 08:01

Dear Dan,

in the thread above about „channel flow with simpleFoam aka simpleChannelFoam“ you wrote
about having problems with convergence of Ubar and gradP.

I'm having the same problem right now (not surprising since I'm using a quite similar solver)
and I'm not able to find the problem.

Have you been able to identify or even solve the problem of the solver you posted?
It would be great to get some feedback :-)

Kind Regards

Tom

chegdan July 11, 2012 10:15

Quote:

Originally Posted by tom ato (Post 370798)
Dear Dan,

in the thread above about „channel flow with simpleFoam aka simpleChannelFoam“ you wrote
about having problems with convergence of Ubar and gradP.

I'm having the same problem right now (not surprising since I'm using a quite similar solver)
and I'm not able to find the problem.

Have you been able to identify or even solve the problem of the solver you posted?
It would be great to get some feedback :-)

Kind Regards

Tom

Dear Tom,

Not yet.

Regards, Dan

tom ato July 16, 2012 06:32

Dear Dan,
Dear Foamers,

the solver posted above by Dan should be correct. A very similar solver
I used is running quite fine by considering the following aspects:

1. it is absolutely vital to use an upwind scheme for solving U (can be changed in the fvSchemes-dictionary if not set by default)

2. relaxationFactors for pressure and velocity must be reduced and should not be bigger than

p 0.15;
U 0.5;

(The relaxation factors can be changed in the fvSolution dictionary)

3. one should take at least 8000 iteration-steps ( set in the controldict-file), although in some cases 4000 iterations might be sufficient as well. I made best experiences with 10000 steps.


In particular, I posted this for Dan in the hope of giving him, and anybody else
having the same problem and reading this thread, an helpful answer, but I fear this is coming to late.

Kind Regards

Tom

chegdan July 16, 2012 07:01

Tom,

Thanks. I'll give it a try and If I can add anything I'll get back here and post it.

Thanks.

Dan


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