beginners questions: black screen, flux values

Post processing utility for Elmer
teobo
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beginners questions: black screen, flux values

Post by teobo » 20 Sep 2014, 07:28

Unbenannt.PNG
(179.1 KiB) Not downloaded yet
Hallo,
just worked through the first tutorial "Heat equation – Temperature field of a
solid object" and everything went fine.

Here are some beginners questions left:
1. I could call the solver from the command line. And it produced an .ep file that I could open with Elmerpost out of the gui. However when I wanted to open it from command line (by just invoking ElmerPost.exe in the very same directory) I got a black screen in the window Elmer Post Graphics. (see screenshot) What can I do?
2. Would like to check the temperature value at a certain point, is not that possible? How?
3 Would like to calculate/check/visualize the heat flux, too. How could that be achieved?

Thanks in advance
Attachments
FEMTUT.zip
(1.07 MiB) Downloaded 258 times
Last edited by teobo on 22 Sep 2014, 03:02, edited 1 time in total.

teobo
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Re: beginners questions: black screen, flux values

Post by teobo » 22 Sep 2014, 03:02

solved at least 1 by trial and error. : Invoking ElmerPost from command line, one need to set Mesh Style and Color Variable.
Still have no clue how to get 2. and 3. Could use some help..
Attachments
Unbenannt2.PNG
Unbenannt2.PNG (20.47 KiB) Viewed 6972 times

raback
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Re: beginners questions: black screen, flux values

Post by raback » 22 Sep 2014, 09:36

Hi

2) You could use SaveScalars solver to write only specific points, or some other postprocessing tool with this feature like Paraview.

3) SaveScalars can also be used to calculate heat fluxes.

-Peter

teobo
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Re: beginners questions: black screen, flux values

Post by teobo » 24 Sep 2014, 00:56

raback wrote:Hi

2) You could use SaveScalars solver to write only specific points, or some other postprocessing tool with this feature like Paraview.

3) SaveScalars can also be used to calculate heat fluxes.

-Peter
Thanks, I will go for it.

btw:
If anybody is interested, here is how I started ElmerPost from command line and the object is displayed without interaction:

ElmerPost source helloworld.txt&
cat helloworld.txt

Code: Select all

set MeshStyle     1
set MeshColor     "Temperature"
rotate 180 0 0
background 90 90 70
set GlobalOptions(VolumeSides) 1
set DisplayStyle(ColorMesh) 1
readfile case.ep
UpdateObject
#DoReadFile case.ep
display
#ReadFileHeader case.ep
#ReadFile
#DoReadFile case.ep 
#mesh_update

teobo
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Re: beginners questions: black screen, flux values

Post by teobo » 02 Oct 2014, 17:57

raback wrote:Hi

2) You could use SaveScalars solver to write only specific points, or some other postprocessing tool with this feature like Paraview.

3) SaveScalars can also be used to calculate heat fluxes.

-Peter
Hello,
here I am back. Learned how to you paraview for postprocessing. Thanks.

As explained I wanted to get to the flux valures.
Manunally editing with vim ElmerGUI/case.sif
such as:

Code: Select all

Solver 3
  Equation = Result Output
  Procedure = File "SaveData" "SaveScalars"
  Output File Name = results
  Output Format = Vtu
  Exec Solver = After Simulation
  Scalar Field 1 = String "Temperature"
  Vector Field 1 = String "Flux"
End


Equation 1
  Name = "Equation 1"
  Active Solvers(3) = 1 2 3
End
brought at least no "test" file. Here the log:
ElmerSolver case.sif >anyname.log 2>&1

Code: Select all

SaveScalars: -----------------------------------------
SaveScalars: Saving scalar values of various kinds
SaveScalars: Performed 0 reduction operations
WARNING:: SaveScalars: Found no values to save
ElmerSolver: *** Elmer Solver: ALL DONE ***
See the my whole files in the attachment.

Questions:
-How to process data the SaveScalars way,
-how do I get to the flux values
-is the a tutorial or an example around for that?
-moreover: how may a get to the overall energy (loss) between to temperature boundaries? (There is where I need to go at the end of day (;)
Thanks in advance
Attachments
case.sif
(2.55 KiB) Downloaded 226 times
anyname.log
(5.77 KiB) Downloaded 197 times

mzenker
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Re: beginners questions: black screen, flux values

Post by mzenker » 02 Oct 2014, 18:16

Hi,

for SaveScalars, you'd best consult the models manual, and do some trial and error with a veeery simple test case where you know the result in advance.
For the heat flux, I would either try to find a way with SaveScalars (calculate the heat flux and save the result with ResultOutputSolver), or use ParaView and try to combine the Gradient filter with the calculator, after having saved the necessary parameters (temperature and thermal conductivity) with ResultOutputSolver.

HTH,

Matthias

mzenker
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Location: Germany

Re: beginners questions: black screen, flux values

Post by mzenker » 02 Oct 2014, 18:28

Hi,

I have just seen in the Models manual that there is a FluxSolver. This seems much easier than the other possibilities I proposed in the last post (haven't tested any of these, though).

HTH,

Matthias

teobo
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Re: beginners questions: black screen, flux values

Post by teobo » 04 Oct 2014, 14:42

Hi,
first I would like to say, that things from my perspective are turning out to get unclear. More and more.
One way to prevent users to bother with bunch question were to provide hello-world examples to any feature.
I mean Elmer, probably great software, seem sparing with it.

for SaveScalars, you'd best consult the models manual, and do some trial and error with a veeery simple test case where you know the result in advance.
I am still using first example for the ElmerGUI tutorial. Ok, thank you! I should have found and read that before asking btw as well, admittedly.

In the models manual one reads:
Manual is a selection of independent chapters describing different modules a.k.a. solvers of the ElmerSolver
Much latin words that one can get something confused. :?
Given that there exists another manual called ElmerSolverManual, this indicates that the functionality FEM-solver is divided
-in a generic part described in the solver manual
-and a modular part described in the modules manual.
Now, I do not understand the design very well at this moment.
But one can say, I believe, that the particular modules issue calculation from the superordinated machine according
a) to the physical problem
b) to the output format.

So my design understanding question:
Is it like that- in order to gain different output formats for different postprocessors (that is 1.Elmerpost, 2.Paraview 3.octave)- I need to deal with each time new physics calculation? It seem uneconomically - It is not everybody's case to study such theory sections such as
48.2 Theory
each time the output formal should be changed (and at breakfeast :) .)
In my case it seems at least like that and it would gratify to read some statement from others.
48.1 Introduction
This subroutine may be used to compute derived quantities and saving scalar values to external file. The
results are easily then utilized by MatLab, Excel or any other program that can read ASCII data.
I assume that this is the main difference to the other modules: It saves it output data in ASCII.
Look my problem: I have in my example 3 modules, each one with different output, but I have no clue how about the physics calculation (among them).
For the heat flux, I would either try to find a way with SaveScalars (calculate the heat flux and save the result with ResultOutputSolver)
I do not understand that.
-SaveScalars is a module and ResultOutputSolver is another module.
-So SaveScalar provides data output for an external calculation programm such as octave? Is it there, where supposedly the heat flux is calculated?
-Where exactly in the data flow gets ResultOutputSolver-module in and what for?

, or use ParaView and try to combine the Gradient filter with the calculator, after having saved the necessary parameters (temperature and thermal conductivity) with ResultOutputSolver.
Thanks for that hint, too. I go for it later.

Thanks in advance for answering.

teobo
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Re: beginners questions: black screen, flux values

Post by teobo » 04 Oct 2014, 17:03

mzenker wrote:Hi,

I have just seen in the Models manual that there is a FluxSolver. This seems much easier than the other possibilities I proposed in the last post (haven't tested any of these, though).

HTH,

Matthias
thanks
ok gonna go for it ..

mzenker
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Joined: 07 Dec 2009, 11:49
Location: Germany

Re: beginners questions: black screen, flux values

Post by mzenker » 06 Oct 2014, 11:11

Hi,
teobo wrote:Hi,
first I would like to say, that things from my perspective are turning out to get unclear. More and more.
This is normal when you start with a complex software... ;)
teobo wrote: One way to prevent users to bother with bunch question were to provide hello-world examples to any feature.
I mean Elmer, probably great software, seem sparing with it.
You have the tutorials, and in addition, you have many examples under $ELMER_HOME\tests.
teobo wrote: So my design understanding question:
Is it like that- in order to gain different output formats for different postprocessors (that is 1.Elmerpost, 2.Paraview 3.octave)- I need to deal with each time new physics calculation? It seem uneconomically - It is not everybody's case to study such theory sections such as
48.2 Theory
each time the output formal should be changed (and at breakfeast :) .)
In my case it seems at least like that and it would gratify to read some statement from others.
There are modules of different kind. You have the modules which do physics calculations and those which do other things, e.g. take care of data saving to different formats. All modules are called "solvers" even though some of them do not actually solve anything. Of course you need to do the physics calculation only once since you can combine different output "solvers" in order to generate the output you need.
teobo wrote: -SaveScalars is a module and ResultOutputSolver is another module.
-So SaveScalar provides data output for an external calculation programm such as octave? Is it there, where supposedly the heat flux is calculated?
-Where exactly in the data flow gets ResultOutputSolver-module in and what for?
SaveScalars has also some calculation functionality, so it can calculate the flux, for example. It adds the results to the internal variable structure, and does not necessarily need to save them to a file. SaveScalars does not know how to write formats like VTK, so you need ResultOutputSolver for that. This is admittedly not very easy to understand. I am also still struggling with this subject...

Elmer is a very powerful software, especially since it is so modular and everyone can make a module which can do virually anything. The Elmer core team is small, so they cannot do everything. Although not perfect, the Elmer documentation is not that bad and already very exhaustive compared to other open source software...

Matthias

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