[2pnc] add useMoles as property to make 2pnc work with new compositional...

[2pnc] add useMoles as property to make 2pnc work with new compositional localresidual and return 0 as diffusion coeffiecient if phaseidx = compIdx instead of warning that diffCoeff does not exist

dumux/porousmediumflow/2pnc/implicit/properties.hh

@@ -75,6 +75,7 @@ NEW_PROP_TAG(EffectiveDiffusivityModel); //!< The employed model for the computa
 NEW_PROP_TAG(ReplaceCompEqIdx); //!< The index of the total mass balance equation, if one component balance is replaced (ReplaceCompEqIdx < NumComponents)
 NEW_PROP_TAG(ProblemEnableGravity); //!< Returns whether gravity is considered in the problem
 NEW_PROP_TAG(BaseFluxVariables); //! The base flux variables
+NEW_PROP_TAG(UseMoles); //!< Defines whether mole (true) or mass (false) fractions are used
 }
 }
 

dumux/porousmediumflow/2pnc/implicit/propertydefaults.hh

@@ -181,6 +181,9 @@ SET_TYPE_PROP(TwoPNC, EffectiveDiffusivityModel, DiffusivityMillingtonQuirk<type
 //! Enable gravity by default
 SET_BOOL_PROP(TwoPNC, ProblemEnableGravity, true);
 
+//! Use mole fractions in the balance equations by default
+SET_BOOL_PROP(TwoPNC, UseMoles, true);
+
 //! Disable velocity output by default
 
 //! Somerton is used as default model to compute the effective thermal heat conductivity

dumux/porousmediumflow/2pnc/implicit/volumevariables.hh

@@ -468,7 +468,7 @@ public:
         else if (compIdx > phaseIdx)
             return diffCoefficient_[phaseIdx][compIdx-1];
         else
-            DUNE_THROW(Dune::InvalidStateException, "Diffusion coeffiecient called for phaseIdx = compIdx");
+            return diffCoefficient_[phaseIdx][compIdx];
     }
 
     /*!
@@ -513,7 +513,7 @@ private:
         else if (compIdx > phaseIdx)
             diffCoefficient_[phaseIdx][compIdx-1] = std::move(d);
         else
-            DUNE_THROW(Dune::InvalidStateException, "Diffusion coeffiecient for phaseIdx = compIdx doesn't exist");
+            diffCoefficient_[phaseIdx][compIdx] = 0;
     }
 
     std::array<std::array<Scalar, numComponents-1>, numPhases> diffCoefficient_;