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 m5m5kh September 5, 2013 06:48

energy equation problem in porousSimpleFoam

Hi dear foamers
I wrote a TEqn for my solver.
the formula is something like thisA. Bejan Convection Heat Transfer,2nd edition, pages 571,575,576)

-dp/dx = [(mu/K) (u)] + [rho*beta*U^2] (darcy-forcheheimer)

and the energy equation is something like this

rho(fluid)*Cp(fluid)[sigma dT/dt + UdT/dx]=k d2T/dx2 + q'" + (mu/K) u^2

k and sigma are:

k= (porosity*kf) + (1- porosity)*ks

Sigma = [porosity(rho*cp)fluid+(1-porosity)*(rho)solid]/(rho*cp)f

for my case there is no heat generation and also I ignored the last term which shows viscous dissipation.
omitting Q"' and (mu/K) u^2, we have :

rho(fluid)*Cp(fluid)[sigma dT/dt + UdT/dx]=k d2T/dx2

dividing both sides of equation to rho(fluid)*Cp(fluid) we have:

[sigma dT/dt + UdT/dx]=alpha d2T/dx2

alpha= k / rho(fluid)*Cp(fluid)

I have all the properties of solid and fluid and porosity,so I can easily define alpha,sigma.I wrote my TEqn.H file like this

// Solve the Energy equation
{
fvScalarMatrix TEqn
(
fvm::ddt(T)
+ fvm::div(phi, T)
- fvm::laplacian(alpha, T)
);
TEqn.solve();

}

I modified createFields.H file either.I defined alpha and sigma in transportProperties file and ask the code to read them from there.

IOdictionary transportProperties
(
IOobject
(
"transportProperties",
runTime.constant(),
mesh,
IOobject::NO_WRITE
)
);

dimensionedScalar sigma
(
transportProperties.lookup("sigma")
);
dimensionedScalar alpha
(
transportProperties.lookup("alpha")
);

Info<< "Reading field T\n" << endl;
volScalarField T
(
IOobject
(
"T",
runTime.timeName(),
mesh,
IOobject::AUTO_WRITE
),
mesh
);

Info<< "Reading field p\n" << endl;
volScalarField p
(
IOobject
(
"p",
runTime.timeName(),
mesh,
IOobject::AUTO_WRITE
),
mesh
);

Info<< "Reading field U\n" << endl;
volVectorField U
(
IOobject
(
"U",
runTime.timeName(),
mesh,
IOobject::AUTO_WRITE
),
mesh
);

#include "createPhi.H"

label pRefCell = 0;
scalar pRefValue = 0.0;
setRefCell(p, mesh.solutionDict().subDict("SIMPLE"), pRefCell, pRefValue);

singlePhaseTransportModel laminarTransport(U, phi);

autoPtr<incompressible::RASModel> turbulence
(
incompressible::RASModel::New(U, phi, laminarTransport)
);

and finally my code is something like this,I used include TEqn.H out of simple loop.

/*---------------------------------------------------------------------------*\
========= |
\\ / F ield | OpenFOAM: The Open Source CFD Toolbox
\\ / O peration |
\\ / A nd | Copyright (C) 2011-2013 OpenFOAM Foundation
\\/ M anipulation |
-------------------------------------------------------------------------------
This file is part of OpenFOAM.

OpenFOAM is free software: you can redistribute it and/or modify it
the Free Software Foundation, either version 3 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, see <http://www.gnu.org/licenses/>.

Application
porousSimpleFoam

Description
Steady-state solver for incompressible, turbulent flow with
implicit or explicit porosity treatment and support for multiple reference
frames (MRF)

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

#include "fvCFD.H"
#include "singlePhaseTransportModel.H"
#include "RASModel.H"
#include "simpleControl.H"
#include "IOMRFZoneList.H"
#include "IOporosityModelList.H"
#include "fvIOoptionList.H"

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

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

simpleControl simple(mesh);

#include "createFields.H"
#include "createFvOptions.H"
#include "createZones.H"
#include "initContinuityErrs.H"

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

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

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

// Pressure-velocity SIMPLE corrector
{
#include "UEqn.H"
#include "pEqn.H"
}

turbulence->correct();

#include "TEqn.H"

runTime.write();

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

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

return 0;
}

// ************************************************** *********************** //
I defined fvscheme and fvsolution file for T equation but I did not understand why this code give me wrong data.

every suggestion would be greatly appreciated.
if anyone has an experienced in this case please send me his/her email.
this error happened after running the code

Time = 0.014

GAMG: Solving for p, Initial residual = 0.964789, Final residual = 0.0417207, No Iterations 17
time step continuity errors : sum local = 2.99708e+12, global = 2.90211e+11, cumulative = 2.90211e+11
DILUPBiCG: Solving for T, Initial residual = 0.994907, Final residual = 0.0487249, No Iterations 22
ExecutionTime = 5.1 s ClockTime = 5 s

Time = 0.015

#0 Foam::error:rintStack(Foam::Ostream&) in "/opt/openfoam220/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#1 Foam::sigFpe::sigHandler(int) in "/opt/openfoam220/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#2 in "/lib/x86_64-linux-gnu/libc.so.6"
#3 at tensorField.C:0
#4
in "/home/vaio/OpenFOAM/vaio-2.2.0/platforms/linux64GccDPOpt/bin/newPorousSimpleFoam"
#5
in "/home/vaio/OpenFOAM/vaio-2.2.0/platforms/linux64GccDPOpt/bin/newPorousSimpleFoam"
#6 __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6"
#7
in "/home/vaio/OpenFOAM/vaio-2.2.0/platforms/linux64GccDPOpt/bin/newPorousSimpleFoam"
Floating point exception (core dumped)
vaio@vaio-SVE14122CVW:~/OpenFOAM/vaio-2.2.0/run/m\$

best regards
Mohsen

 AJAY BHANDARI August 3, 2015 06:16

Hi mohsen,

By seeing your second error it looks like you are giving some wrong BC. check your BC again. and in your divison terms some (0/0) term is becoming thats why sigpe error is coming.

Regards
Ajay

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