# FSI Wall Expansion Problem

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 April 18, 2012, 20:56 FSI Wall Expansion Problem #1 Senior Member   Ashkan Javadzadegan Join Date: Sep 2010 Posts: 248 Rep Power: 9 Sponsored Links Dear All, I did steady FSI in a straight pipe with 50pa inlet pressure and 0 outlet pressure. Someone else for his thesis did the same simulation few years ago, there is a big difference between my results and his results. For me, the pipe wall is expanded close to inlet and outlet, however, for him, the wall is expanded in the middle of the pipe. Does anybody know where the problem originates from. An image regarding this issue is attached. http://imageshack.us/photo/my-images/217/fsi1.jpg/ Kind regards, AshtonJ

April 19, 2012, 00:45
#2
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Gwenael H.
Join Date: Mar 2011
Location: Switzerland
Posts: 155
Rep Power: 11
Dear Ashkan,

How did you create your geometry, and can you be more specific about your problem setup. If you have the exact same setup you should find the same, from your image I suppose that your BC aren't well imposed.

I'm investigating the static instability of your pipe conveying fluid using Ansys 14, if your setup is done properly you can have some results like buckling.
Attached Images
 FSIpipe.jpg (25.0 KB, 22 views)

 April 19, 2012, 01:04 #3 Senior Member   Ashkan Javadzadegan Join Date: Sep 2010 Posts: 248 Rep Power: 9 Dear Gweher, Thanks for your reply. Let me explain my problem. I am doing steady FSI in a simple straight pipe. Pipe length: 8cm Diameter: 2cm Wall thickness: 0.1cm The material of the wall is: Young module: 10MPa Poisson ratio: 0.3 Density: 1050 kg/m^3 Structural setting Hex dominant (Quad) mesh with 1188 Elements Analysis Settings: Autotime stepping: Off Define by: substeps Number of substeps: 1 Time Integration: Off Boundary Conditions: Inlet and outlet: Fixed support Inner surface of the wall: Fluid-solid interface Fluid setting Hex dominant (Quad) mesh with 8800 Elements Boundary Conditions: Inlet: Static Pressure 50Pa Outlet: Static Pressure 0Pa Wall: fluid-solid interface Initial conditions: Automatic Solver Control: Fluid part: Advection scheme: High resolution transient scheme :Second order backward max loops: 100 convergence criteria:0.0001 Structural part: max iteration: 25 Under relaxation factor: 0.75 Convergence target: 0.01 I went through all the thesis settings and am sure that I used the same settings. Kind regards, AshtonJ

 April 19, 2012, 03:36 #4 Senior Member     Gwenael H. Join Date: Mar 2011 Location: Switzerland Posts: 155 Rep Power: 11 When you imposed your boundary condition (Structural) did you select the inner radius edge, the outer edge or the surface thickness? If you send me your files I can have a quick look.

 April 19, 2012, 04:43 #5 Senior Member   Ashkan Javadzadegan Join Date: Sep 2010 Posts: 248 Rep Power: 9 Thank you very much for your kind attention. Can I have your email address plz to send my case. I am in the Uni and here I don't have access to the file sharing website like Rapishare. Kind regards, AshtonJ

 April 19, 2012, 07:14 #6 Senior Member     Gwenael H. Join Date: Mar 2011 Location: Switzerland Posts: 155 Rep Power: 11 I've send you an e-mail, I'll try to have a look tomorrow.

 April 19, 2012, 08:04 #7 Senior Member   Ashkan Javadzadegan Join Date: Sep 2010 Posts: 248 Rep Power: 9 Thank you very much. The file is sent. Kind regards, AshtonJ

 November 26, 2012, 10:12 #8 New Member   Khardith Join Date: Sep 2012 Posts: 2 Rep Power: 0 Hi Ashkan, I am also working a very similar geometry as yours by using ANSYS CFX V12 solver. I was wondering if you have figured out how to solve the boundary conditions that you mentioned here? Or, was that the boundary issues that caused your mesh deformation different than the one simulated by the author? Thank you.

 December 5, 2012, 08:07 #9 Senior Member   Govindaraju Join Date: Apr 2010 Posts: 207 Rep Power: 10 Dear friend I am working on similar problem . I am doing transient two fsi problem. I don't know how to do Analysis settings in the transient structural Kindly help me to figure out time step , number of steps etc Regards Govind

 December 5, 2012, 08:18 #10 Senior Member   Govindaraju Join Date: Apr 2010 Posts: 207 Rep Power: 10 Dear friend I confuse with step control settings. Is it necessary for pulsatile flow through the pipe? Regards Govind

December 5, 2012, 14:19
#11
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Khardith
Join Date: Sep 2012
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Quote:
 Originally Posted by kmgraju Dear friend I confuse with step control settings. Is it necessary for pulsatile flow through the pipe? Regards Govind
I Govind, for the structural part, ANSYS CFX Tutorial - Chap.23 for FSI may give you some idea how to set it up. For my case, the only change I made was instead of using timestep, i used Substeps. and no. of substep=1. I hope this helps. May i know what is your topic about?

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