[StefanP]

Dear FOAMers,
i want to couple the mass flow of an outlet BC to the inlet BC, thus I modified the pressureInletVelocity BC.
My problem is that the scalar outflow doesn't work and I can't use it.

The code looks as follows:
{
if (updated())
{
return;
}

const surfaceScalarField& rhoPhi =
db().lookupObject<surfaceScalarField>("rhoPhi");

const volScalarField& rho =
db().lookupObject<volScalarField>("rho");

tmp<vectorField> n = patch().nf();

const fvMesh& mesh = patch().boundaryMesh().mesh();

label couplingPatchID = mesh.boundaryMesh().findPatchID(couplingPatchName_ );

const Field<scalar>& magS = patch().magSf();

const fvPatchField<scalar>& rho_Patch = patch().lookupPatchField<volScalarField, scalar>(rhoName_);


if (rhoPhi.dimensions() == dimVelocity*dimArea*dimDensity)
{
const fvsPatchField<scalar>& outflow = sum(rhoPhi.boundaryField()[couplingPatchID]);

const scalar S_patch = sum(magS);

operator==(n*outflow/S_patch);

Info<< "mass flux = " <<outflow << endl <<endl;
}
else
{
FatalErrorInFunction
<< "dimensions of phi are not correct"
<< "\n on patch " << this->patch().name()
<< " of field " << this->internalField().name()
<< " in file " << this->internalField().objectPath()
<< exit(FatalError);
}

fixedValueFvPatchVectorField::updateCoeffs();
}

Can anyone help me with that problem?

THANK YOU IN ADVANCE

[nimasam]

why don't you use cyclic boundary condition ?

[StefanP]

Thank you very much nimasam for your quick answer!
I think the way I wanted to tackle the problem was too complicated

[StefanP]

But regardless of using cyclic boundary condition would be the better choice, what is the problem in my coded BC?

[luther1990]

Originally Posted by StefanP

But regardless of using cyclic boundary condition would be the better choice, what is the problem in my coded BC?

What is couplingPatchName_?

First, you need to make sure couplingPatchID is correct.

Second, in the following code, outflow is defined as fvsPatchField, which is not a scalar. Also, sum(rhoPhi.boundaryField() makes no sense.

const fvsPatchField<scalar>& outflow = sum(rhoPhi.boundaryField()[couplingPatchID]);

const scalar S_patch = sum(magS);

operator==(n*outflow/S_patch);

I am not sure what version are you using, but in OF30x, it already implemented

    else if (phi.dimensions() == dimDensity*dimVelocity*dimArea)
    {
        const fvPatchField<scalar>& rhop =
            patch().lookupPatchField<volScalarField, scalar>(rhoName_);

        operator==(n*phip/(rhop*magS));
    }

Hope it can help you.