[io] make vtk output module independent of fluid system

Geomechanical models will not be able to reuse the vtk output module
otherwise.

dumux/discretization/staggered/freeflow/velocityoutput.hh

@@ -78,6 +78,10 @@ public:
     bool enableOutput()
     { return velocityOutput_; }
 
+    // returns the name of the phase for a given index
+    static std::string phaseName(int phaseIdx)
+    { return GET_PROP_TYPE(TypeTag, FluidSystem)::phaseName(phaseIdx); }
+
     //! Return the problem boundary types
     auto problemBoundaryTypes(const Element& element, const SubControlVolumeFace& scvf) const
     { return problem_.boundaryTypes(element, scvf); }

dumux/io/vtkoutputmodule.hh

@@ -72,7 +72,6 @@ class VtkOutputModule
     static constexpr int numPhases = ModelTraits::numPhases();
 
     using VV = typename GridVariables::VolumeVariables;
-    using FluidSystem = typename VV::FluidSystem;
     using Scalar = typename GridVariables::Scalar;
 
     using GridView = typename FVGridGeometry::GridView;
@@ -381,7 +380,7 @@ private:
                 {
                     for (int phaseIdx = 0; phaseIdx < numPhases; ++phaseIdx)
                         sequenceWriter_.addVertexData( Field(gridGeom_.gridView(), gridGeom_.vertexMapper(), velocity[phaseIdx],
-                                                             "velocity_" + std::string(FluidSystem::phaseName(phaseIdx+phaseIdxOffset)) + " (m/s)",
+                                                             "velocity_" + velocityOutput.phaseName(phaseIdx+phaseIdxOffset) + " (m/s)",
                                                              /*numComp*/dimWorld, /*codim*/dim).get() );
                 }
                 // cell-centered models
@@ -389,7 +388,7 @@ private:
                 {
                     for (int phaseIdx = 0; phaseIdx < numPhases; ++phaseIdx)
                         sequenceWriter_.addCellData( Field(gridGeom_.gridView(), gridGeom_.elementMapper(), velocity[phaseIdx],
-                                                           "velocity_" + std::string(FluidSystem::phaseName(phaseIdx+phaseIdxOffset)) + " (m/s)",
+                                                           "velocity_" + velocityOutput.phaseName(phaseIdx+phaseIdxOffset) + " (m/s)",
                                                            /*numComp*/dimWorld, /*codim*/0).get() );
                 }
             }
@@ -549,14 +548,14 @@ private:
                 if (dim > 1)
                     for (int phaseIdx = 0; phaseIdx < numPhases; ++phaseIdx)
                         sequenceWriter_.addVertexData( Field(gridGeom_.gridView(), gridGeom_.vertexMapper(), velocity[phaseIdx],
-                                                             "velocity_" + std::string(FluidSystem::phaseName(phaseIdx+phaseIdxOffset)) + " (m/s)",
+                                                             "velocity_" + velocityOutput.phaseName(phaseIdx+phaseIdxOffset) + " (m/s)",
                                                              /*numComp*/dimWorld, /*codim*/dim).get() );
 
                 // cell-wise velocities
                 else
                     for (int phaseIdx = 0; phaseIdx < numPhases; ++phaseIdx)
                         sequenceWriter_.addCellData( Field(gridGeom_.gridView(), gridGeom_.elementMapper(), velocity[phaseIdx],
-                                                           "velocity_" + std::string(FluidSystem::phaseName(phaseIdx+phaseIdxOffset)) + " (m/s)",
+                                                           "velocity_" + velocityOutput.phaseName(phaseIdx+phaseIdxOffset) + " (m/s)",
                                                            /*numComp*/dimWorld, /*codim*/0).get() );
             }
 

dumux/porousmediumflow/velocityoutput.hh

@@ -48,6 +48,7 @@ class PorousMediumFlowVelocityOutput
     using SubControlVolumeFace = typename FVElementGeometry::SubControlVolumeFace;
     using ElementVolumeVariables = typename GET_PROP_TYPE(TypeTag, GridVolumeVariables)::LocalView;
     using VolumeVariables = typename GET_PROP_TYPE(TypeTag, VolumeVariables);
+    using FluidSystem = typename GET_PROP_TYPE(TypeTag, FluidSystem);
     using FluxVariables = typename GET_PROP_TYPE(TypeTag, FluxVariables);
     using BoundaryTypes = typename GET_PROP_TYPE(TypeTag, BoundaryTypes);
     using GridView = typename GET_PROP_TYPE(TypeTag, GridView);
@@ -106,6 +107,10 @@ public:
     bool enableOutput()
     { return velocityOutput_; }
 
+    // returns the name of the phase for a given index
+    static std::string phaseName(int phaseIdx)
+    { return FluidSystem::phaseName(phaseIdx); }
+
     // The following SFINAE enable_if usage allows compilation, even if only a
     //
     // boundaryTypes(const Element&, const scv&)