[Transport] Make optional the dispersion write

doc/default_files/transport-parameters.xml

@@ -67,6 +67,16 @@ adding an empty line, make text **bold** or ``monospaced``.
       <values> endOfTransportStep, endOfRichardsStep, none </values>
     </parameter>
 
+    <parameter name="writeDispersionTensor">
+      <definition> Defines whether VTK files should include the hydrodynamic 
+       dispersion tensor. Tensors are written in 3D and have 9 componentents 
+       independently of the world dimension. This can be easily be visualizated
+       in Paraview with the ``Tensor Glyph`` filter.
+      </definition>
+      <values> true, false </values>
+      <suggestion> false </suggestion>
+    </parameter>
+
     <parameter name="subsamplingLevel">
       <definition> Plot VTK files with virtually refined grids. VTK only
         supports bilinear triangulations and displays higher-order solutions

dune/dorie/model/transport/transport.cc

@@ -229,6 +229,8 @@ void TransportSimulation<Traits>::write_data () const
       vtkwriter->template addVertexData<GFSolute>(get_solute(),"solute");
       vtkwriter->template addVertexData<GFTotalSolute>(get_total_solute(),"total_solute");
       vtkwriter->template addVertexData<GFPeclet>(peclet,"micro_peclet");
+      
+      if (inifile.get<bool>("output.writeDispersionTensor"))
         vtkwriter->template addVertexData<GFEffectiveHydrodynamicDispersion>(d_hd,"eff_hd_dispersion");
 
       if constexpr (enable_rt_engine)
@@ -241,7 +243,10 @@ void TransportSimulation<Traits>::write_data () const
       vtkwriter->template addCellData<GFSolute>(get_solute(),"solute");
       vtkwriter->template addCellData<GFTotalSolute>(get_total_solute(),"total_solute");
       vtkwriter->template addCellData<GFPeclet>(peclet,"micro_peclet");
+      
+      if (inifile.get<bool>("output.writeDispersionTensor"))
         vtkwriter->template addCellData<GFEffectiveHydrodynamicDispersion>(d_hd,"eff_hd_dispersion");
+      
       if constexpr (enable_rt_engine)
         if (enable_fluxrc) {
           auto RT_name = "flux_RT" + std::to_string(flux_order);

test/const_solute.mini.in

@@ -40,6 +40,7 @@ output.fileName = {__name}
 output.outputPath = {__name}
 output.vertexData = false
 output.policy = endOfRichardsStep
+output.writeDispersionTensor = true
 
 boundary.file = "{_asset_path}/bcs/solute_2d_const.dat"