CFD Online Discussion Forums - Don't understand solver's behaviour

Hello guys,

today I'm facing a problem, which I can't explain. I have done a dummy calculation for a variable f. f is set everywhere to 1 (boundary/internal). Nevertheless OpenFOAM calculates values differing from 1. Can anyone explain that behaviour to me? Thank you very much in advance.

I have a normal transport equation for variable f:

Code:

    f_(

        IOobject

        (

            "f",

            mesh.time().timeName(),

            mesh,

            IOobject::MUST_READ,

            IOobject::AUTO_WRITE

        ),

        mesh

    ),

dimensions [0 0 0 0 0 0 0];

Boundary and internal values all set to 1.

Code:

  multivariateSurfaceInterpolationScheme<scalar>::fielTable fields;

    fields.add(f);



    tmp<fv::convectionScheme<scalar> > convection

    (

        fv::convectionScheme<scalar>::New

        (

            mesh_,

            fields,

            phi,

            mesh_.divScheme("div(phi,f)")

        )

    );

So again keep in mind, for testing purpose I set all values to 1. Now I'm trying to solve the following equations:

Code:

Info << "fmin/max   = " << min(f_).value() << ", " << max(f_).value() << endl;;



tmp<fvScalarMatrix> fEqn

(

    fvm::ddt(rho, f_)

    +  convection->fvmDiv(phi, f_)

    -  fvm::laplacian(turbulence_->alphaEff(), f_)

);

fEqn().relax();



solve(fEqn == rho* fSource);

fSource is set to 0.

Code:

Info << "fmin/max = " << min(f_).value() << ", " << max(f_).value() << endl;;

The Output is:

f min/max = 1, 1
f min/max = 0.90082369, 1.1320949

Schemes:

laplacian(alphaEff,f) Gauss linear corrected;
div(phi,f) Gauss upwind;

RASModel kEpsilon;