flux/porenetwork/fickslaw.hh

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#ifndef DUMUX_FLUX_PNM_FICKS_LAW_HH
#define DUMUX_FLUX_PNM_FICKS_LAW_HH
 
#include <dune/common/fvector.hh>
#include <dumux/common/math.hh>
#include <dumux/flux/referencesystemformulation.hh>
#include <dumux/flux/fickiandiffusioncoefficients.hh>
 
namespace Dumux::PoreNetwork {
 
template<class Scalar, int numPhases, int numComponents,
         ReferenceSystemFormulation referenceSystem = ReferenceSystemFormulation::massAveraged>
class PNMFicksLaw
{
public:
    using DiffusionCoefficientsContainer = FickianDiffusionCoefficients<Scalar, numPhases, numComponents>;
 
    //return the reference system
    static constexpr ReferenceSystemFormulation referenceSystemFormulation()
    { return referenceSystem; }
 
    template<class Problem, class Element, class FVElementGeometry,
             class ElementVolumeVariables, class ElementFluxVariablesCache>
    static Dune::FieldVector<Scalar, numComponents>
    flux(const Problem& problem,
         const Element& element,
         const FVElementGeometry& fvGeometry,
         const ElementVolumeVariables& elemVolVars,
         const typename FVElementGeometry::SubControlVolumeFace& scvf,
         const int phaseIdx,
         const ElementFluxVariablesCache& elemFluxVarsCache)
    {
        Dune::FieldVector<Scalar, numComponents> componentFlux(0.0);
 
        // get inside and outside diffusion tensors and calculate the harmonic mean
        const auto& insideVolVars = elemVolVars[scvf.insideScvIdx()];
        const auto& outsideVolVars = elemVolVars[scvf.outsideScvIdx()];
 
        const auto& fluxVarsCache = elemFluxVarsCache[scvf];
 
        const Scalar density = 0.5 * (massOrMolarDensity(insideVolVars, referenceSystem, phaseIdx) + massOrMolarDensity(outsideVolVars, referenceSystem, phaseIdx));
        const Scalar throatLength = fluxVarsCache.throatLength();
        const Scalar phaseCrossSectionalArea = fluxVarsCache.throatCrossSectionalArea(phaseIdx);
 
        for (int compIdx = 0; compIdx < numComponents; compIdx++)
        {
            if(compIdx == phaseIdx)
                continue;
 
            auto insideDiffCoeff = getDiffusionCoefficient_(phaseIdx, compIdx, insideVolVars);
            auto outsideDiffCoeff = getDiffusionCoefficient_(phaseIdx, compIdx, outsideVolVars);
 
            // scale by extrusion factor
            insideDiffCoeff *= insideVolVars.extrusionFactor();
            outsideDiffCoeff *= outsideVolVars.extrusionFactor();
 
            // the resulting averaged diffusion coefficient
            const auto diffCoeff = harmonicMean(insideDiffCoeff, outsideDiffCoeff);
 
            const Scalar insideMoleFraction = massOrMoleFraction(insideVolVars, referenceSystem, phaseIdx, compIdx);
            const Scalar outsideMoleFraction = massOrMoleFraction(outsideVolVars, referenceSystem, phaseIdx, compIdx);
 
            componentFlux[compIdx] = density * (insideMoleFraction - outsideMoleFraction) / throatLength * diffCoeff * phaseCrossSectionalArea;
            componentFlux[phaseIdx] -= componentFlux[compIdx];
        }
        return componentFlux;
    }
private:
 
    template<class VolumeVariables>
    static Scalar getDiffusionCoefficient_(const int phaseIdx, const int compIdx,
                                           const VolumeVariables& volVars)
    {
        using FluidSystem = typename VolumeVariables::FluidSystem;
 
        if constexpr (!FluidSystem::isTracerFluidSystem())
        {
            const auto mainCompIdx = FluidSystem::getMainComponent(phaseIdx);
            return volVars.diffusionCoefficient(phaseIdx, mainCompIdx, compIdx);
        }
        else
            return volVars.diffusionCoefficient(0, 0, compIdx);
    }
};
} // end namespace Dumux::PoreNetwork
 
#endif