[Benben]

Hello,

I am trying to modify reactingFoam from openfoam 6.0 so that i can save the flux of species.

I created a volScalarField to save this value

volVectorField flux_N2
(
    IOobject
    (
        "flux_N2",
        runTime.timeName(),
        mesh,
        IOobject::READ_IF_PRESENT,
        IOobject::AUTO_WRITE
    ),
    mesh,
    dimensionedVector("flux_N2_0", dimensionSet(1,-2,-1,0,0,0,0), Foam::vector(0,0,0))
);

And i modified YEqn.h to save the flux of N2:

//Saving Zn flux
if (Yi.name() == "N2")
{
    flux_Zn = rho*U*Yi - rho*D_i*fvc::grad(Yi)();
}

My problem is that this returns a volVectorField, and i want the flux for each cell face. How can i obtain a similar volSurfaceField ?

[Santiago]

Have you tried snGrad?

[Benben]

Hello, thank you for your help.

Unfortunately, it seems that snGrad returns a surfaceScalarField and not a surfaceVectorField. It returns a scalar because it seems to perform a dot product of the gradient with the normal to the cell.

[Benben]

I found this post regarding the calculation of the gaussGrad.
It seems to be possible to calculate the vector at the interface, but not with high level functions.

[Santiago]

Originally Posted by Benben

Hello, thank you for your help.

Unfortunately, it seems that snGrad returns a surfaceScalarField and not a surfaceVectorField. It returns a scalar because it seems to perform a dot product of the gradient with the normal to the cell.

You asked for a face flux, which is a scalar. If you multiply such scalar by the surface area normal you get the flux by components.

If you want the gradient at the face centre, calculate it using fvc::grad and then interpolate the vector to the face centre. I dont see other way that doesnt involve creating a dual mesh