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June 2, 2013, 20:01 |
rotation inconsistent error
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#1 |
New Member
Manjunath
Join Date: Dec 2012
Location: Salt Lake City, Utah, USA
Posts: 14
Rep Power: 13 |
Hello,
I am trying to simulate flow in a stirred tank using symmetry assumption. I am considering only half volume(180 section of the tank). I am able to successfully create periodic faces in Fluent for rotating and stationary zones. But, fluent is not able to get the correct rotation angle and gives error everything I do mesh check (attached image). I specify the rotational periodicity in ICEM with proper angle and rotation axis. I have tried rotating the geometry and mesh in ICEM and Fluent but I still get the error but the "average rotation angle" changes. I have attached the screenshot of the error message. Can someone please help me with this issue. I have been struggling with this for the last 2 weeks without knowing the cause of the error. Thanks, Manjunath |
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June 3, 2013, 05:18 |
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#2 |
Senior Member
Philipp
Join Date: Jun 2011
Location: Germany
Posts: 1,297
Rep Power: 26 |
I always create a "normal" mesh in ICEM, without bothering ICEM with any periodicity. This takes all place in Fluent and I never had any problem like this. Maybe you should try: Switch off all periodic stuff in ICEM and just name the relevant surfaces. Export to fluent and do everything here.
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June 3, 2013, 14:27 |
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#3 |
New Member
Manjunath
Join Date: Dec 2012
Location: Salt Lake City, Utah, USA
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I did try doing that but still got the same error. BTW, I was able to set up the problem in Fluent despite the error. I will proceed with the simulation and see if it makes any difference to the results. Thanks for your reply.
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June 4, 2013, 02:57 |
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#4 |
Senior Member
Philipp
Join Date: Jun 2011
Location: Germany
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How do you set up Fluent? With "make-periodic" in the terminal?
Maybe your mesh isn't conformal, i.e. the cell faces don't fit together...
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June 4, 2013, 14:48 |
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#5 |
New Member
Manjunath
Join Date: Dec 2012
Location: Salt Lake City, Utah, USA
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I use the make-periodic TUI to set up the periodic faces. The faces are conformal and the number of cells on both the faces match exactly. Infact, I was able to set up and the run the case for 120 degree section earlier. But, when I started out with 180 degree section I started facing the average rotation issue in Fluent. I have run out of things to change on ICEM and Fluent side to see where the problem is. I suspect the periodic faces lying on a straight line might cause rotation problem, but people have simulated such problems before so I am not sure.
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June 5, 2013, 03:50 |
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#6 |
Senior Member
Philipp
Join Date: Jun 2011
Location: Germany
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Did you run "make-periodic" with and without automatic angle detection?
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June 5, 2013, 11:53 |
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#7 |
New Member
Manjunath
Join Date: Dec 2012
Location: Salt Lake City, Utah, USA
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I think it would be without automatic angle detection. I use the following commands: define> boundary-conditions> modify-zones> make-periodic>
followed by zone names. I have not come across the make-periodic option with and without automatic angle detection in Fluent. Can you tell me the exact command or post a link so that I can read more about it. Thanks for your response. |
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June 5, 2013, 12:41 |
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#8 |
Senior Member
Rick
Join Date: Oct 2010
Posts: 1,016
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Hi,
first of all, but I think it's a typo, symmetry condition is not good, as you have to use periodic condition. I had also these problems in the past, check: 1- in pre-processor the rotation axis: I remember in the past I had the axis not perfectly centered in 0,0,0, but something like 10^-7,0,0: copy these values into fluent for axis origin 2- so, in fluent the rotation axis is set up properly Daniele |
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June 5, 2013, 12:49 |
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#9 |
New Member
Manjunath
Join Date: Dec 2012
Location: Salt Lake City, Utah, USA
Posts: 14
Rep Power: 13 |
Hi Daniele,
What I meant by symmetry was that I would be using periodic conditions and use only half of the tank volume because of the flow symmetry. I created the periodic faces as walls in ICEM and used Fluent to assign periodicity using make-periodic. I will check to make sure I am assigning the rotation axis origin properly in ICEM and Fluent. Thanks for your help. Regards, Manjunath |
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June 6, 2013, 01:56 |
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#10 |
Senior Member
Philipp
Join Date: Jun 2011
Location: Germany
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Manjunath, I only use translational symmetry, but I am asked by fluent whether I want to auto-detect the offset or put it in by hand. (during the "make-periodic"). Your respond sounds like fluent doesn't ask you...
Why don't you upload the ICEM files?
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June 6, 2013, 12:16 |
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#11 |
New Member
Manjunath
Join Date: Dec 2012
Location: Salt Lake City, Utah, USA
Posts: 14
Rep Power: 13 |
https://www.dropbox.com/sh/dm1o4itd38fzhpf/tHHBgYrPgr
Here is the link for geometry and blocking files for rotor and stator zones. Daniele, I checked to make sure I was entering the correct values for origin and axis but I got a similar error again. Thanks, Manjunath |
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June 7, 2013, 04:13 |
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#12 |
Senior Member
Philipp
Join Date: Jun 2011
Location: Germany
Posts: 1,297
Rep Power: 26 |
error in xxx.tin
can't read surface model. Any ideas? I use Icem 14.5.
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June 12, 2013, 05:23 |
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#13 |
Senior Member
Philipp
Join Date: Jun 2011
Location: Germany
Posts: 1,297
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Alright, as I said, I only had translational periodicity before, but it seems that in Fluent you need the periodic axis to be the z-axis. Once I rotated the blocks and geometry I could use "make-periodic". Also, I had problems to import the mesh, when faces were called "periodic-blabla". I changed their name to "pe-blabla" and it worked.
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