[ngbidi]

Hi Foamers,

Usually I set the option "constantEmissivity" in the view factor radiation model to true because I used the lookup model with constant emissivity in the past. Recently I implemented a submodel for boundaryProperties such that the emissivity changes over time so I started to look more into this option.
Apparently the emissivity still changes over time when setting constantEmissivity to true. This is because the function to update the emissivity is called regardless of the option:

In radiation::viewFactor::calculate()

 const tmp<scalarField> teb = boundaryRadiation.emissivity(patchID, bandI);

constantEmissivity is then used later to do some calculations:

Also in radiation::viewFactor::calculate()

            if (!constEmissivity_)
            {
                scalarSquareMatrix C(totalNCoarseFaces_, 0.0);

                for (label i=0; i<totalNCoarseFaces_; i++)
                {
                    for (label j=0; j<totalNCoarseFaces_; j++)
                    {
                        const scalar invEj = 1.0/E[j];
                        const scalar sigmaT4 =
                            physicoChemical::sigma.value()*T4[j];

                        if (i==j)
                        {
                            C(i, j) = invEj - (invEj - 1.0)*Fmatrix_()(i, j);
                            q[i] +=
                                (Fmatrix_()(i, j) - 1.0)*sigmaT4 + qrExt[j];
                        }
                        else
                        {
                            C(i, j) = (1.0 - invEj)*Fmatrix_()(i, j);
                            q[i] += Fmatrix_()(i, j)*sigmaT4;
                        }

                    }
                }

                Info<< "Solving view factor equations for band :"
                    << bandI << endl;

                // Negative coming into the fluid
                LUsolve(C, q);
            }
            else //Constant emissivity
            {
                // Initial iter calculates CLU and caches it
                if (iterCounter_ == 0)
                {
                    for (label i=0; i<totalNCoarseFaces_; i++)
                    {
                        for (label j=0; j<totalNCoarseFaces_; j++)
                        {
                            const scalar invEj = 1.0/E[j];
                            if (i==j)
                            {
                                CLU_()(i, j) =
                                    invEj-(invEj-1.0)*Fmatrix_()(i, j);
                            }
                            else
                            {
                                CLU_()(i, j) = (1.0 - invEj)*Fmatrix_()(i, j);
                            }
                        }
                    }

                    DebugInFunction << "\nDecomposing C matrix..." << endl;

                    LUDecompose(CLU_(), pivotIndices_);
                }

                for (label i=0; i<totalNCoarseFaces_; i++)
                {
                    for (label j=0; j<totalNCoarseFaces_; j++)
                    {
                        const scalar sigmaT4 =
                            constant::physicoChemical::sigma.value()*T4[j];

                        if (i==j)
                        {
                            q[i] +=
                            (Fmatrix_()(i, j) - 1.0)*sigmaT4  + qrExt[j];
                        }
                        else
                        {
                            q[i] += Fmatrix_()(i, j)*sigmaT4;
                        }
                    }
                }


                Info<< "Solving view factor equations for band : "
                    << bandI  << endl;


                LUBacksubstitute(CLU_(), pivotIndices_, q);
                iterCounter_ ++;
            }

I don't understand what is going on in this part. When testing both options, qr is twice as high when setting constantEmissivity to false.
Does anyone know more about this?

Thanks in advance!