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Old   January 20, 2008, 17:46
Default two way fluid structure interaction
  #1
mike
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i am trying to model an oscillating wing in CFX. i know how to create an structural simulation however i am not sure on how to create a CFX mesh for the fluid-structure interaction. i've tried using the tutorials but the CFX mesh for the solver was already created.

if anyone knows how to to create the CFX mesh your assistance will be appreciated.

thanks
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Old   January 22, 2008, 04:06
Default Re: two way fluid structure interaction
  #2
Gen
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Hi! If you haven't got CFX-Mesh license you can use ANSYS to make mesh for CFX calculation. Just make fluid domain geometry model (using your solid model), generate grid and archive your db-file to *.cdb. This file can be imported in CFX. If you have got Ansys Workbench you can use CFX-Mesh. Open in Main Menu Tools/Options/Meshing/Meshing and set in Default Physics Preference - CFD and in Default Method - CFX-Mesh. After that just open WB mesh generator. Good luck!
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Old   January 22, 2008, 21:59
Default Re: two way fluid structure interaction
  #3
mike
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I know how to do a mesh with CFX but with the solver i get the following errors:

ERROR #001100279 has occurred in subroutine ErrAction. | | Message: | | CFX encountered the error: Read. Fatal error occurred when reque- | | sting Total Mesh Displacement for interface.

ERROR #001100279 has occurred in subroutine ErrAction. | | Message: | | cplg_SendCommand failed to send the command: ERROR -- CFX encount- | | ered the error: Read. Fatal error occurred when requesting Total | | Mesh Displacement for interface.

ERROR #001100279 has occurred in subroutine ErrAction. | | Message: | | Stopped in routine cplg_SendCommand | |

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Old   February 9, 2008, 20:04
Default Re: two way fluid structure interaction
  #4
alfin
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hi mike

i got the same error did u get any response

i think may be we have to refine the mesh

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Old   February 10, 2008, 17:40
Default Re: two way fluid structure interaction
  #5
Glenn Horrocks
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Hi,

I suspect the error is in the definition of the mesh movement, not the mesh quality or refinement. I would check the mesh motion is properly defined in CFX-Pre.

Glenn Horrocks
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Old   February 12, 2008, 00:32
Default Re: two way fluid structure interaction
  #6
mike
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Hi,

I was able to fix my input file however I get a new error saying a folded mesh has occurred. Which mesh is the referring to the structural or the CFX surface?
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Old   February 12, 2008, 06:57
Default Re: two way fluid structure interaction
  #7
Glenn Horrocks
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Hi,

If you output some timesteps to a results file you should be able to see the mesh fold.

Glenn Horrocks
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Old   February 13, 2008, 11:00
Default Re: two way fluid structure interaction
  #8
Anna Davis
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Hi guys I'm afraid I can't help you guys but you are seemingly further than me at making this program do its thang.

I've run tutorial 21 in CFX 11.0 and am now trying to run a simulation for a mesh which I have as a cgns file. This is obviously fine for CFX however I was wondering if you knew ways that I could make the cgns file useable in ansys for the structural solving?

Any help would be greatly appreciated.

Anna Davis
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Old   February 14, 2008, 16:27
Default Re: two way fluid structure interaction
  #9
alfin
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hi mike

how did u fix this error fatal error in calculating total mesh displacement could you please help me out

any small piece of information will be very helpful

ALFIN
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Old   February 16, 2008, 18:34
Default Re: two way fluid structure interaction
  #10
alfin
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hi glenn

i checked the mesh definition i could not fix it. could you be more precise in what i have to do.i trying with all possible combinations still the same error at the same step

i would appreciate if u can suggest me something
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Old   November 21, 2012, 16:37
Default Two-way FSI of brain Injury
  #11
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Hesam Moghaddam
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Dear Sir/Madam,

I want to model the head injury by using FSI. I am taking a simple model of three circular-shaped parts. First a thin layer representing skull, then a thin layer representing cerebrospinal fluid and finally a circle representing brain. they are all extruded for one millimeter in z- direction and are simulated as 2D by choosing just one element on z direction.


I want to apply a force, pressure, displacement or velocity on the outer surface of the skull and see what happens to the fluid and the brain surrounded by that flow. So we have two solid parts and one solid. The materials of solids are different. skull has a density of 1940 kg/m^3 and brain has density of 1060 kg/m^3. the dimensions considered are in smaller scales such as a diameter of D = 30 mm for skull and D = 20 mm for brain. Both materials are considered elastic with Young's modulus of E= 16 GPa for skull and E = 600 MPa for brain.


the fluid is laminar and steady. there is no moving fluid. actually consider it as a volume of fluid. The properties of the fluid are exactly as water. I have defined 2 fluid-solid interface in both Tranisent structural and CFX and matched them correctly based on your tutorial on oscillating plate.


I applied symmetry on both lateral faces of my fluid body to provide correct conditions in terms of 2D simulation.


So far, I have only been able to apply velocity on the outer surface of the skull and initial velocity on the skull. Any other thing such as pressure and force and displacements caused the program to exit with error saying that CFX cannot get Total Mesh displacement from ANSYS.


My main questions are as follow:


1- Based on the problem statement, I realized I should use two-way FSI, Am I right?




2- Is two -way FSI only obtained through Transient structural with one of the Fluid flow options (CFX or Fluent)? or there is another mechanical option that can be coupled with CFX or Fluent to provide two -way FSI?




3- My main problem is that in my problem I may have both fluid-solid interaction and contact of solid parts together. you know, I mean that when when apply force on skull, it causes pressure on the fluid and based on the acuity of the impact, this pressure may cause the brain to move rapidly in the fluid and may hit the skull on the other end. In my limited progress, I have managed to see the movement of brain inside the fluid. after some time I hits the other endof the skull and this is when it exits with the same error. I know that it should be because it can't simulate contact which defines my next probelm.




4- I have tried to see the contact of my two solid bodies in ANSYS Transient Structural. I gave an initial velocity to the skull to make it contact with brain in form of an impact but I get ridiculous answers which shows that skull and brain faces merge into together!!!! I have tried all types of contacts but there is no answer!!!! what should i do? IS IT POSSIBLE TO SIMULATE IMPACT IN TRANSIENT STRUCTURAL?




5- Next thing is that I managed to simulated the impact i mentioned in question 4 in Explicit Dynamics and see that after skull hits the brain, it goes forward and backward as it hits the walls of skull. The option that does that in Explicit Dynamics is Body Interaction option defined under Contacts.


But there is not such as thing in Transient structural!


How can i manage to do the same thing in transient structural?




6- and Finally, Is it possible to do any two-way FSI using Explicit Dynamics coupled with any Fluid Flow option such as CFX or Fluent?




Becuse all the example of impacts that I have seen in ANSYS tutorials or training materials have mainly been done using Explicit dynamics.


I have done all the steps using ANSYS Transient Structural and CFX and changed the timestep and refined the mesh but I constantly get the error" Fatal error occurred when requesting Total Mesh Displacement for Interface1"

I really appreciate your comprehensive help and response to my questions as I am really stuck.


Thanks,


Hesam
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