[dune-pdelab] Instationary Navier-Stokes equations with Finite Volume method : Getting the velocity components at the center of the faces

[CERRITO Samuel]

Hi,

I wrote my own Local Operator to achieve a finite volume method on the instasionary Navier-Stokes equations.
I also coded the associated Local Functions (localBasis, localcoefficients and LocalInterpolation) to have a proper finite element map.

The problem is I DON'T want to get my velocity components on the vertices BUT on the center of the faces of my cells.

To do so, I tried to start form the cgstokes case in which the addVertexData is used.

I looked into the VTKWriter.hh file but couldn't find out how to change the position where to get my data (from vertex to center of face)...

In my LocalInterpolation.hh file, I use the following function :

template<typename F, typename C>
      void interpolate (const F& f, std::vector<C>& out) const {
        typename LB::Traits::DomainType x;
        typename LB::Traits::RangeType y;

        out.resize(4);
        x[0] = 0.5; x[1] = 0.0; f.evaluate(x,y); out[0] = y; // out[] should be 1 or 2
        x[0] = 0.0; x[1] = 0.5; f.evaluate(x,y); out[1] = y;
        x[0] = 1.0; x[1] = 1.0; f.evaluate(x,y); out[2] = y;
        x[0] = 0.5; x[1] = 1.0; f.evaluate(x,y); out[3] = y;
      }


In my Main, I have the following lines :

 //////////////////////////////////////////////////////////
  // Initial guess
  Dune::PDELab::FilenameHelper fn(filename); //output file name
  {
    // Generate functions suitable for VTK output
    typedef Dune::PDELab::VectorDiscreteGridFunction<VelocitySubGFS,V> VDGF;
    VDGF vdgf(velocitySubGfs,x0);
    typedef Dune::PDELab::DiscreteGridFunction<PressureSubGFS,V> PDGF;
    PDGF pdgf(pressureSubGfs,x0);

    // Output grid function with SubsamplingVTKWriter
    Dune::SubsamplingVTKWriter<GV> vtkwriter(gv,2);
    vtkwriter.addCellData(new Dune::PDELab::VTKGridFunctionAdapter<PDGF>(pdgf,"p")); // get pressure
    vtkwriter.addVertexData(new Dune::PDELab::VTKGridFunctionAdapter<VDGF>(vdgf,"v")); // get velocity
    vtkwriter.write(fn.getName(),Dune::VTK::ascii);//appendedraw); // write ouput file
    std::cout << "VTK output file was written: " << fn.getName() << ".vtu" << std::endl;
    fn.increment(); // increment output file name
  }

Thx for your help !

Samuel
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