[2pdfm] mobility update in the volume variables

After updating the matrix saturations in the interface condition the mobilities in the matrix have to be updated. This is essential in the dfm approach and was not implemented.

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

@@ -211,6 +211,20 @@ public:
         porosityFracture_ = problem.spatialParams().porosityFracture(element,
                                                                   fvGeometry,
                                                                   scvIdx);
+
+        // After modifying the Matrix saturations we have to update the fluid state and the matrix mobilities
+        PrimaryVariables updatedMatrixPV;
+        updatedMatrixPV[pressureIdx] = priVars[pressureIdx];
+        updatedMatrixPV[saturationIdx] = satWMatrix_;
+        this->completeFluidState(priVars, problem, element, fvGeometry, scvIdx, fluidState_);
+
+        mobilityMatrix_[wPhaseIdx] =
+            MaterialLaw::krw(materialParamsMatrix, satWMatrix_)
+            / fluidState_.viscosity(wPhaseIdx);
+
+        mobilityMatrix_[nPhaseIdx] =
+            MaterialLaw::krn(materialParamsMatrix, satWMatrix_)
+            / fluidState_.viscosity(nPhaseIdx);
     }
 
     /*!