Thanks, Daniel: Yes, this won't work since FEValues need a cell to reinit to get mapping data. I looded at the class DataPostprocessor as you mentioned, but don't quite understand the parameters passed to compute_derived_quantities_vector method. I don't understand what exactly is the parameters "uh", "duh" ..., I know they are the computed finite element solutions, but I don't how they are composed, so I don't know how to use them.
As I have stated in the first post, I want to compute the stress using dierivatives of the solution, namely <https://lh3.googleusercontent.com/-HucFvD1_fXU/V0J7dsthOEI/AAAAAAAAACo/lQkFJ2oHzaw7FaOxMqAOwNLr-7CgKw34gCLcB/s1600/constitutive.png> so how can I use it to compute u_k,k, u_i,j and u_j,i., does these quantities the same with the parameter "duh" ? Could you (or anyone else) please give some explanation? Great thanks! Best regards, David. On Monday, May 23, 2016 at 3:23:46 AM UTC+8, Daniel Arndt wrote: > > David, > > the code snippet you posted is not going to work. You can't use a FEValues > without initializing it with a cell_iterator. > If all the information you need for your postprocessing is contained in a > data vector based on a single DoFHandler, then DataPostprocessor is what > you want to use. > If you take a look at the interface at the signature of > DataPostprocessor<dim>::compute_derived_quantities_scalar[1], you see that > this provides the access you want. > Namely, you access at the vertices of the patches used for output. > > Best, > Daniel > -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
