[TeddyL]

Hello!

I am using OpenFOAM-v2212, and trying to understand the boundary condition: fixedFluxPressure. But I find the code rather strange, as it calls member functions from a class that seems does not exist (fixedGradientFvPatchScalarField). I searched in the API guide only to find a class named "fixedGradientFvPatchField". How could this code possibly run without errors? I think it may be a version-related issue, but I still can't understand.

in fixedFluxPressureFvPatchScalarField.C:

void Foam::fixedFluxPressureFvPatchScalarField::updateSnGrad
(
    const scalarField& snGradp
)
{
    if (updated())
    {
        return;
    }
 
    curTimeIndex_ = this->db().time().timeIndex();
 
    gradient() = snGradp;
    fixedGradientFvPatchScalarField::updateCoeffs();
// could it probably be fixedGradientFvPatchField?
}

Thanks for any help!

[Tobermory]

The answer is a little subtle. Class fixedGradientFvPatchScalarField is the implementation of the fixedGradientFvPatchField class, for a scalar field (the field type is the class parameter). It is generated in fixedGradientFvPatchFields.H (https://www.openfoam.com/documentati...8H_source.html), which calls a macro in fvPatchField.H
(https://www.openfoam.com/documentati...ce.html#l00715) to generate the class.

That's why you can't find it in Doxygen, or with a grep on the src folder.

[dlahaye]

The dependency graph at https://www.openfoam.com/documentati...rField_8H.html
does show that fixedFluxPressureFvPatchScalarField does call fixedGradientFvPatchScalarField.

Not sure how this complements what Tobermory provides as information.

[TeddyL]

Wow, Thank You, Tobermory!! It really helped! I never thought it would be a generate class.

[TeddyL]

Originally Posted by dlahaye

The dependency graph at https://www.openfoam.com/documentati...rField_8H.html
does show that fixedFluxPressureFvPatchScalarField does call fixedGradientFvPatchScalarField.

Not sure how this complements what Tobermory provides as information.

Yes! Thank you! I think I got it, the fixedFluxPressureFvPatchScalarField calls fixedGradientFvPatchFields, which calls fixedGradientFvPatchField to generate a new class based on Scalar type