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Rigid body motion on transient fluent mrf

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Old   September 1, 2014, 09:54
Default Rigid body motion on transient fluent mrf
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Rick
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Hi!
I'm just testing the Ensight software and first impressions are very positive.
I like the rigid body motion option to rotate mrf cases.

I tried the rigid body motion setup on a single couple of cas/dat (fluent) mrf and it works well.

I cannot get rigid body motion to work with a mrf transient solution (I simulated a stirred tank with vof in fluent, a transient simulation to explore the vortex formation).

What I did is:
1- Export from fluent solutions to ensight gold format: this generated files: 1 .encas, 1 .geo, 1 .vel and several sclxxx (for the variables I chosed)
2- Start Ensight and open the .encas file (the ensight window shows a transient solution made of 14 time steps, 0 to 13); I can create the isosurface to animate the free surface morphology with no problem
3- Select the impeller zone, click on user tools, visualize, rigid body motion: set the center of rotation, axis direction, set rpm to 120, 14 time steps and flow time to 1,3 s (which is the end of the simulation) and chose the existing .encas file
4- This generate _rbm.case, _rbm.eet and _rbm.erb files in the working directory

Instead of the popup window which should ask to reload the case with rbm enable nothing happens
If I try to load the new generated _rbm.case an error shows unable to load data.

So my question is: how to correctly setup the rigid body motion for a transient mrf simulation?

Thank you!
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Old   September 2, 2014, 08:30
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Kevin Colburn
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Looks like you did all as you should. It sounds like an error in the RBM Setup tool. I suspect this has to do with the handling of the timesets already in the original .encas file (which you did not have in the steady state which worked okay). If you could send me a private email with just your original .encas file, and the new .encas file (which does not work), I think it should be an easy fix (just need to allow for the logic of the timesets already in the original .encas file.

-Kevin
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Old   September 2, 2014, 09:05
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Thans for fast reply.
I will write as soon as possible with attached files.
Yes, I agree with you, I thought about a time step conflicting problem.
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Old   September 3, 2014, 04:05
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Just for reference if someone else has same problems.
The error was in the eet file.
Number of time steps must be the same as the transient fluent simulation (which in my case was 14).
However, setting the same number of time steps (14) in the rmb gui in ensight did not work, the eet was created with 37 time steps (bug?).
The solution is to manually edit the eet file, so to set the right number of time steps.
Thanks to Kevin for fast reply and solution to the problem.

I think he (and the team) is working on the bugfix (if any).
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Old   September 6, 2014, 11:24
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I noticed that the eet file is always created with a number of time steps of +23 in respect of what is specified by default (which is the correct value) in the rbm gui.
Maybe this is usefull for the bug fix.

EDIT:
Bug is fixed and it will be corrected in version 10.1.1(d).

Last edited by ghost82; September 14, 2014 at 11:34.
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