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Initializing transient analysis using static analysis in two-way FSI simulation

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Old   April 30, 2014, 13:35
Default Initializing transient analysis using static analysis in two-way FSI simulation
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Daniel
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Hello to all

I am planning to do fluid-structure interaction using Fluent an structural in workbench.

I know how to setup transient and static two-way FSI separately. However I don't know how to use static analysis results as an initial condition for transient analysis to make it stable.

Is it possible to do it in workbench interface?


any help would be appreciated

Best wishes,
Danial Khazaei
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Old   May 3, 2014, 12:14
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any help?

Best wishes
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Old   May 5, 2014, 02:40
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Dear Daniel,

Unfortunately i do not know how to solve your problem, but i think that you can help me. I see that you solved static 2 way FSI. Please, give me some advise how to setup this problem. My problem based on calculating lift force on flexible wing.

Thank you in advance,
sf
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Old   May 11, 2014, 12:37
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Quote:
Originally Posted by skinnyfluid View Post
Dear Daniel,

Unfortunately i do not know how to solve your problem, but i think that you can help me. I see that you solved static 2 way FSI. Please, give me some advise how to setup this problem. My problem based on calculating lift force on flexible wing.

Thank you in advance,
sf
I have gone through system coupling tutorials in order to learn how to setup a case for two-way FSI problem.


Best wishes
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Old   May 12, 2014, 11:14
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Daniel,

Is it necessary to write UDF for defining "Deforming" option within "Geometry Definition"? This zone (geometry) surrounding wing geometry (interior field).

Thanks,
sf
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Old   May 12, 2014, 17:24
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Quote:
Originally Posted by skinnyfluid View Post
Daniel,

Is it necessary to write UDF for defining "Deforming" option within "Geometry Definition"? This zone (geometry) surrounding wing geometry (interior field).

Thanks,
sf
Do you need a prescribed motion for the wing?
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Old   May 13, 2014, 06:01
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I want to calculate the resulting wing deformation caused by aerodynamic simulation and than lift over deformed wing (fluent-->mechanical-->fluent, with system coupling). Calculated lift force over deformed wing is about 20 % lesser then over rigid configuration and this is pretty realistic situation. It is static 2-way fsi, isn't it?

Thank you Daniel for conversation.
All the best.
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Old   May 13, 2014, 09:41
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Quote:
Originally Posted by skinnyfluid View Post
I want to calculate the resulting wing deformation caused by aerodynamic simulation and than lift over deformed wing (fluent-->mechanical-->fluent, with system coupling). Calculated lift force over deformed wing is about 20 % lesser then over rigid configuration and this is pretty realistic situation. It is static 2-way fsi, isn't it?

Thank you Daniel for conversation.
All the best.
Yes it's a two-way fsi simulation.
Regarding the deformation:

1) prescribed motion of wing like plunging and pitching: you need to write a UDF

2) deformation of wing due to aerodynamic forces only: no need for UDF
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Old   May 14, 2014, 12:19
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Ok, thank you very much.
What is about flutter - need or no need for UDF?
Did you overcome your problem (how to use static analysis results as an initial condition for transient analysis)? I have read some proposal that solves the problem. It is all about Time Integration ON/OFF within Analysis Settings - try with OFF in 1st second to reach static condition and go forward with transient starting from 1st second.
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Old   May 29, 2014, 06:49
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Quote:
Originally Posted by skinnyfluid View Post
Ok, thank you very much.
What is about flutter - need or no need for UDF?
Did you overcome your problem (how to use static analysis results as an initial condition for transient analysis)? I have read some proposal that solves the problem. It is all about Time Integration ON/OFF within Analysis Settings - try with OFF in 1st second to reach static condition and go forward with transient starting from 1st second.
Sorry for the late response. I was too busy with rest of my works.

Do you need the flutter to move based on the prescribed motion?

---------

Regarding my question, what I understand is:

1) setting up Fluent and transient structural for two coupling.

2) in order to obtain steady-state solution:

a) Turning off Time Integration in transient structural.
b) Steady-state in Fluent

3) after obtaining the solution, start the real transient analysis.

Am I correct?


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Old   June 2, 2014, 18:58
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Correct, but, sorry, I was wrong Daniel. That proposal is for CFX, so, Mechanical don't allow to conduct transient simulation by setting up prestress on that way (within system coupling environment). Try this way:
1) connect (export) steady (converged and saved) fluent with transient fluent
2) connect transient fluent (without initializing) with system coupling engine
3) connect transient structural (with Time Integration ON) with sys coupl eng
4) within sys coupl (Co-Sim. Sequence) set trans struct to do first sequence and fluent 2nd

I'm not sure but I think that you want to do this. I did it.
Inform me about your progress.
Good luck.
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Old   June 3, 2014, 02:01
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Quote:
Originally Posted by skinnyfluid View Post
Correct, but, sorry, I was wrong Daniel. That proposal is for CFX, so, Mechanical don't allow to conduct transient simulation by setting up prestress on that way (within system coupling environment). Try this way:
1) connect (export) steady (converged and saved) fluent with transient fluent
2) connect transient fluent (without initializing) with system coupling engine
3) connect transient structural (with Time Integration ON) with sys coupl eng
4) within sys coupl (Co-Sim. Sequence) set trans struct to do first sequence and fluent 2nd

I'm not sure but I think that you want to do this. I did it.
Inform me about your progress.
Good luck.
Thank you.

Yes I have tried that method and system coupling does not allow transient mechanical with stead-state Fluent.

----

Your new suggestion seems reasonable, I will try it soon.


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Old   June 4, 2014, 05:47
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I have another problem regarding mapping summery in system coupling log file.
It reports 0 percent mapped on both sides of FSI interface.

I have generated the fluid mesh in ICEM, then I have deleted the volume mesh.
After that, surface mesh of FSI interface on fluid side is extruded in order to get solid wall volume mesh.

I have tested both mesh with OpenFOAM FSI solver and it reports an almost zero interpolation error at the interface (1.2e-17)
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Old   June 4, 2014, 10:58
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Share some images of your problem, please. I'm not sure I understand your problem well. What does it mean "...I have deleted the volume mesh"? Do you want to simulate some hemodynamics problem? Please, depict your problem.
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Old   June 4, 2014, 11:55
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Quote:
Originally Posted by skinnyfluid View Post
Share some images of your problem, please. I'm not sure I understand your problem well. What does it mean "...I have deleted the volume mesh"? Do you want to simulate some hemodynamics problem? Please, depict your problem.
Yes, I am planning to perform a fluid-structure interaction in a vessel.

1) fluid mesh is generated in ICEM (att, fluid)

2) surface mesh which is the same on both sides (fluid & solid). (att, surfaceMesh)

3) solid mesh is the generated by extruding the surface mesh by an specific thickness.

However, it seems that system coupling is unable to read that and mapping summery reports 0 percent mapped.
Attached Images
File Type: jpg fluid.jpg (96.6 KB, 8 views)
File Type: jpg surfaceMesh.jpg (82.0 KB, 4 views)
File Type: jpg solid.jpg (96.2 KB, 4 views)
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Old   June 5, 2014, 11:01
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Check which side of the wall you selected to be Fluid Solid Interface in Mechanical (inner or outer wall of the vessel). I saw hemodynamics simulation with system coupling. It works.
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Old   June 14, 2014, 06:18
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Quote:
Originally Posted by skinnyfluid View Post
Check which side of the wall you selected to be Fluid Solid Interface in Mechanical (inner or outer wall of the vessel). I saw hemodynamics simulation with system coupling. It works.
I think I have found the problem, however I don't have any alternatives. You can see the project schematic in the att. I have tried with much simpler problem which I have tested with the same method of system coupling tutorial and it worked. However, after using my current project schematic on it, I get 0 percent area mapped here too.

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Old   June 18, 2014, 02:46
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Did you try to break and resetup the very last connection? Maybe also delete the *.ds file from ansys (which is basically the same as the first).
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Old   June 18, 2014, 06:45
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Quote:
Originally Posted by mvoss View Post
Did you try to break and resetup the very last connection? Maybe also delete the *.ds file from ansys (which is basically the same as the first).
Thank you. I will try to test your suggestion.
However I did not understand the second part of your suggestion regarding deleting the *.ds file from ansys.

Thanks in advance.

--------

edit:

I have tried the first part of your suggestion with no luck. I still get 0 percent area mapped.

Last edited by Daniel_Khazaei; June 18, 2014 at 07:46.
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Old   June 30, 2014, 10:02
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any help?


Best wishes
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