dolfin team mailing list archive

["Garth N. Wells" <g.n.wells@xxxxxxxxxx>]

pcorreia@xxxxxxxxx wrote:
> > On Mon, Jun 11, 2007 at 01:40:50PM -0400, Harish Narayanan wrote:
> > > pcorreia@xxxxxxxxx wrote:
> > > > In the Stokes demo the velocity solution is written as a vtk file
> > > > velocity000000.vtu.
> > > > How can I plot each of the components say u and v (I use Paraview)?
> > > And
> > > > how to plot the vector field?
> > > Assuming you've opened the file velocity.pvd in Paraview:
> > >
> > > 1. In order to plot the vector field, add a "glyph" from the filter menu
> > > and point it to the velocity vector (U) as the data source. You can
> > > change the glyph density, size, shape, etc.
> > > 2. In order to plot a scalar, such as a velocity component or a norm, I
> > > use the "calculator" filter. Click calculator, and you can refer to the
> > > components as U_0 and U_1. So if you wanted to plot the velocity norm,
> > > you'd "calculate" norm (U) and plot the result, and if you wanted to
> > > just plot a component, you'd just use U_0 or U_1.
> > >
> > > Harish
> > You should also be able to extract the components in DOLFIN and then
> > save (or plot) each one of them:
> >
> >   Function u0 = u[0];
> >   Function u1 = u[1];
> >
> > Then
> >
> >   plot(u0);
> >   plot(u1);
> >
> > should plot the two components as scalar fields. Or save each one to
> > VTK format if you don't have Viper.
>
>
>
> I added this but it gives an error:
>
>   // Solve PDE
>   Function u;
>
>   Function u0 = u[0];
>   Function u1 = u[1];

The above two lines shouldn't be here. They should be after pde.solve(...);

Garth

>   Function p;
>   pde.set("PDE linear solver", "direct");
>   pde.solve(u, p);
>
>   // Plot solution
>   plot(u);
>   plot(p);
>
>   plot(u0);
>   plot(u1);
>
>   // Save solution
>   File ufile("velocity.xml");
>   ufile << u;
>   File pfile("pressure.xml");
>   pfile << p;
>
>   // Save solution in VTK format
>   File ufile_pvd("velocity.pvd");
>   ufile_pvd << u;
>   File pfile_pvd("pressure.pvd");
>   pfile_pvd << p;
>
>   File u0_file_pvd("u.pvd");
>   u0_file_pvd << u0;
>   File u1_file_pvd("v.pvd");
>   u1_file_pvd << u1;
>
>
> $>./demo
> Initializing PETSc (ignoring command-line arguments).
> Creating linear PDE with 3 boundary condition(s).
> terminate called after throwing an instance of 'std::runtime_error'
>   what():  *** Error: Sub functions can only be extracted from discrete
> functions.
> p0_8737:  p4_error: interrupt SIGx: 6
>
>
>
>
>
>
>
> > /Anders
> > _______________________________________________
> > DOLFIN-dev mailing list
> > DOLFIN-dev@xxxxxxxxxx
> > http://www.fenics.org/mailman/listinfo/dolfin-dev
>
>
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