Like Paul said, Exodus II would be the easiest way to get a visual representation of the divergence.
I also need to correct what I said earlier. If you want to represent the divergence of the solution (which is in L2) in the same nodal basis as the solution, i.e. let f = div(u_h), and F = sum f_i * phi_i its representation. Building a new system with RHS = f * phi_j , Kij = phi_i * phi_j and solve this new system, the resulting solution would be a projection of div(u_h) and its nodal values would correspond to f_i. No need to do anything with the rhs vector. The patch recovery error estimator already present in libMesh already does this, but at a local level. Thanks. On Thu, Jul 23, 2015 at 11:22 AM, Vikram Garg <vikram.v.g...@gmail.com> wrote: > One way to do this might be to create a new system where the divergence at > the continuous level is the right hand side. Then you can repeat the usual > assembly of the RHS using the loop over elems, dofs and qps, using your > existing solution. > > You could then swap the rhs vector with one of the components of the > solution vector and print that out in the usual way using > Tecplot/Paraview/etc IO, see for example the plotting of the adjoint > solutions in Adjoints Example 1. > > On Wed, Jul 22, 2015 at 6:13 PM, Sahai, Amal <sah...@illinois.edu> wrote: > >> I have a system with 3 variables, representing the x,y,z component of a >> quantity. I solved this system to obtain the component wise distribution in >> a given domain. I would now like to calculate the divergence of this >> distribution at the node points and then output this along with the >> previous 3 variables. How do I compute the divergence at the node points? I >> could only find routines for derivatives of the shape functions at the >> quadrature points. >> >> Regards >> Amal >> >> >> >> ------------------------------------------------------------------------------ >> _______________________________________________ >> Libmesh-users mailing list >> Libmesh-users@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/libmesh-users >> > > > > -- > Vikram Garg > Postdoctoral Associate > Predictive Engineering and Computational Science (PECOS) > The University of Texas at Austin > http://web.mit.edu/vikramvg/www/ > > http://vikramvgarg.wordpress.com/ > http://www.runforindia.org/runners/vikramg > -- Vikram Garg Postdoctoral Associate Predictive Engineering and Computational Science (PECOS) The University of Texas at Austin http://web.mit.edu/vikramvg/www/ http://vikramvgarg.wordpress.com/ http://www.runforindia.org/runners/vikramg ------------------------------------------------------------------------------ _______________________________________________ Libmesh-users mailing list Libmesh-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/libmesh-users
