Proper way of outputting nodal AuxVariables to exodus

[john.m...@uconn.edu]

Hello

I've noticed that since I've updated MOOSE from about June, the default exodus file output no longer captures node values for AuxVariables that I am computing. I've been looking through the literature online and the ./apt-opt --dump function and can't seem to locate how to turn this back on. I'm using the following AuxVariables and AuxKernels blocks

[AuxVariables]

  [./stress_xx]
    order = CONSTANT
    family = MONOMIAL
  [../]
[]

[AuxKernels]

  [./stress_xx]
    type = RankTwoAux
    rank_two_tensor = stress
    variable = stress_xx
    index_i = 0
    index_j = 0
  [../]
[]

and the Outputs block

[Outputs]
  [./Exodus]
    type = Exodus
    file_base = out
    output_nodal_variables = 1
    output_elemental_variables = 1
    output_initial = 0
  [../]
  [./console]
    type = Console
    perf_log = true
    linear_residuals = true
  [../]
[]

Surely its a quick fix, but I've tried quite a few things to no avail.
Thanks
John

[Slaughter, Andrew E]

The AuxVariable that you have is an elemental, so it should show up as an elemental variable in your exodus. You can convert this to a nodal variable by adding 'elemental_as_nodal = true' in your [./Exodus] block.

--
You received this message because you are subscribed to the Google Groups "moose-users" group.
To unsubscribe from this group and stop receiving emails from it, send an email to moose-users...@googlegroups.com.
Visit this group at http://groups.google.com/group/moose-users.
To view this discussion on the web visit https://groups.google.com/d/msgid/moose-users/39a1333b-626a-49c6-832d-093076181111%40googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

[Slaughter, Andrew E]

I am looking at this further and this might not work with AuxVariables, I will investigate more and get back with you.

[Slaughter, Andrew E]

My suggest should work, the test: /moose/test/tests/outputs/exodus/exodus_nodal.i is doing this. Some of the documentation and member variable names are misleading; I will get that fixed up.

[john.m...@uconn.edu]

Your suggestion did indeed work. A follow-up problem is that now my elemental values are replaced by the nodal values. How do I keep both of them(on the same Exodus file) with this method?

Thanks.

[Slaughter, Andrew E]

They should both show up, if you execute the test I mentioned and set 'output_elemental_variables = true' both show up, at least they show up in both Peacock and Paraview.

To view this discussion on the web visit https://groups.google.com/d/msgid/moose-users/b4916832-7ab8-4382-8495-1c6734047a3e%40googlegroups.com.

[john.m...@uconn.edu]

Andrew,

Thanks again. The follow-up problem actually didn't happen. I think I just failed to update my reader. At any rate, just so I know, was this a change that was introduced into MOOSE sometime recently? Default on the old Legacy version gives both the nodal and elemental values.

John

[Derek Gaston]

I'll let Andrew talk about the changes... but I want to make sure you're aware that these "nodal" fields that are created this way are "projections" of your elemental field.

Specifically - they are the average values at the nodes (taken from the value of each adjoining element).

Be careful using that kind of value for "science".  The elemental field is the "true" representation of the solution...

Derek

To view this discussion on the web visit https://groups.google.com/d/msgid/moose-users/a28f290b-ebd6-4f47-a612-3f62609a1138%40googlegroups.com.

For more options, visit https://groups.google.com/d/optout.

--
Sent from my iPhone

[Slaughter, Andrew E]

The new Outputs system was implemented in early March. This change was a complete re-write of the output system. Your input file now uses an [Outputs] block instead of an [Output] block, notice the "s". This change on the behavior of outputting both nodal and elemental values for AuxVariables was made then. As Derek mention the nodal values of an elemental field are projections, thus when the new system was implemented none of this type of projection output is enabled by default, because it is can be misleading.

For more information on the Outputs system see http://www.mooseframework.org/wiki/MooseSystems/Outputs/

-Andrew

To view this discussion on the web visit https://groups.google.com/d/msgid/moose-users/CAFfxPjqwai9LBuCYRCZhSpDmBOCUtUEK9K6rnB8WOzB0oy1K5A%40mail.gmail.com.