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reactingFoam without reaction

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Old   April 11, 2016, 07:27
Default reactingFoam without reaction
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Adrien ORSINI
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Hi foamers,

I'm running reactingFoam without reaction in order to simulate a flow of CH4 into another flow of air (N2+02).
The thing is, when I run the solver, "rho" isn't solved.
I've post a photo of two successive iteration of what I get on terminal. As you can see, rho doesn't seems to be resolved because without any iteration.

FIRST:
Does it means that reactingFoam isn't a compressible solver (but I can't believe it because of the purpose of this solver...)

SECOND:
Does it mean that my set up isn't okay ? Here is my file fvSolution

Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.2.2                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    location    "system";
    object      fvSolution;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

solvers
{
    "rho.*"
    {
        solver          diagonal;
    }

    p
    {
        solver           PCG;
        preconditioner   DIC;
        tolerance        1e-6;
        relTol           0.1;
    }

    pFinal
    {
        $p;
        tolerance        1e-6;
        relTol           0.0;
    }

    "(U|h|k|epsilon)"
    {
        solver          PBiCG;
        preconditioner  DILU;
        tolerance       1e-6;
        relTol          0.1;
    }

    "(U|h|k|epsilon)Final"
    {
        $U;
        relTol          0;
    }

    Yi
    {
        $hFinal;
    }
}

PIMPLE
{
    momentumPredictor no;
    nOuterCorrectors  1;
    nCorrectors     2;
    nNonOrthogonalCorrectors 2;
}


// ************************************************************************* //
THIRD:
Should I use the solver rhoPimpleFoam instead of PimpleFoam ?
Attached Images
File Type: jpg reactingFoam.jpg (204.7 KB, 11 views)
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Old   April 11, 2016, 09:10
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Yan Wang
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That's no problem. The reason is

Code:
    "rho.*"
    {
        solver          diagonal;
    }
and

Code:
    fvScalarMatrix rhoEqn
    (
        fvm::ddt(rho)
      + fvc::div(phi)
      ==
        fvOptions(rho)
    );
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Old   April 11, 2016, 09:24
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Adrien ORSINI
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Thank you for your reply Wayne14, but in fact, I don't see what's ok (or not).

Do you wanna mean that the solver "diagonal" isn't good for a scalar wich appeared in equation "on time" like this fvm::ddt(rho)

Could you explain to me more precisely ?

Thank you for your time again Wayne14,
Adrien
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Old   April 11, 2016, 10:19
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Yan Wang
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Hi Adrien,

When you solve Ax=b, if A is a diagonal matrix, then you would not need any iteration to solve for x.

fvm::ddt(x) + fvc:: anything gives exactly a diagonal matrix.

So it is correct.

Yan
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Old   April 11, 2016, 11:26
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Adrien ORSINI
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Aaaa ok (I feel stupid ) ! Thank you for this explanation.
But... in fact, I tried before to run my case (I mean a quite easier but quit closed case) with rhoPimpleFoam in order to "approach" a compressible solver.
And with rhoPimpleFoam I had some iterations on rho.
It means that physical equations involved with those two solvers (rhopimplefoam & reactingfoam but without reaction) are not the same ?
And as a result, does it means that reactingFoam isn't fitting well for my case (with wrong hypothesis)... ?

Any hints/clue would be very welcomed,
Thank you
Adrien
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Old   June 2, 2016, 11:29
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Mr.liu
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Quote:
Originally Posted by wayne14 View Post
Hi Adrien,

When you solve Ax=b, if A is a diagonal matrix, then you would not need any iteration to solve for x.

fvm::ddt(x) + fvc:: anything gives exactly a diagonal matrix.

So it is correct.

Yan
I meet a problem in Openfoam 2.3.0, reactingFoam, i need the data of CH4 reaction rate, but i failed to autowrite it like U or Yi.

First i added this code in the CreatField.H,

volScalarField Rrate
(
IOobject
(
"Rrate",
runTime.timeName(),
mesh,
IOobject::NO_READ,
IOobject::AUTO_WRITE
),
mesh,
dimensionedScalar("Rrate", dimMass/dimVolume/dimTime, 0.0)
);

Then, i added this code in YEqn,

forAll(Y, i)
{
if (Y[i].name() != "CH4")
RR = reaction->R(Yi);
}

After wmake, it shows

YEqn.H:26:14: error: no match for ‘operator=’ (operand types are ‘Foam::volScalarField {aka Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh>}’ and ‘Foam::tmp<Foam::fvMatrix<double> >’)
Rrate = reaction->R(Yi);

Can you tell me how to do that? Thank you very much.
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