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[solved]problem when decomposing velocity flux according to the x, y and z directions

Hi!

I would like to decompose the velocity flux phi into 3 flux, one for each direction:

Code:

phi = phi_x + phi_y + phi_z

To do that, I defined phi_x, phi_y and phi_z as:

Code:

surfaceScalarField phi_x = linearInterpolate(U.component(vector::X)*vector(1,0,0)) & mesh.Sf();

surfaceScalarField phi_y = linearInterpolate(U.component(vector::Y)*vector(0,1,0)) & mesh.Sf();

surfaceScalarField phi_z = linearInterpolate(U.component(vector::Z)*vector(0,0,1)) & mesh.Sf();

Then I update these fields at each time step with the above definition. However, the field

Code:

phiTest = phi - (phi_x+phi_y+phi_z)

is not equal to "zero". Which (I suppose) yields in divergence for my applications...

Is someone know how to do such a thing ?

I was wondering is there is a way to get these fields from the fvScalarMatrix pEqn exactly in the same manner we update the phi flux field :
In OpenFOAM, we get the phi flux from the pEqn matrix:

Code:

fvScalarMatrix pEqn

(

    fvm::laplacian(-M,p)

);

pEqn.setReference (....);

pEqn.solve();

phi = pEqn.flux();

I was wondering is there is a way to get these fields (phi_x, phi_y, phi_z) from the fvScalarMatrix pEqn in similar manner ??

Best regards,
Cyp

PS: in my example, M is a volTensorField

I found a solution : from phi = pEqn.flux() I can create phix, phiy and phiz.

First, I defined a flux phi_ex with 1 on the faces concerning x and 0 elsewhere. I can create this flux with this snippet:

Code:

    volVectorField E

    (

        IOobject

        (

            "E",

            runTime.timeName(),

            mesh,

            IOobject::NO_READ,

            IOobject::AUTO_WRITE

        ),

        mesh,

       dimensionedVector ("E",dimensionSet(0,0,0,0,0),vector::zero)

    );

    E = vector(1,0,0);

    surfaceScalarField phi_ex = linearInterpolate(E) & mesh.Sf() / mesh.magSf();

then I can get phix from phi using :

Code:

phix = phi * phi_ex;

And I repeat the operation for y and z.

However, I still have problem on my outlet BC....