CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > FLUENT

FSI Valve - Biomedical application

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   May 26, 2015, 18:20
Default FSI Valve - Biomedical application
  #1
New Member
 
Join Date: Apr 2013
Posts: 6
Rep Power: 12
jtwilson is on a distinguished road
Hi All,

I am currently wanting to perform an FSI simulation with a biomedical valve geometry using system coupling - I've lately been receiving errors stating that fluent fails due to negative elements. T'm using a Neo-Hookean model with an initial shear modulus of 90kPa. The simulation is '2D' in nature, however my fluid domain has a thickness in the third dimension - I just apply symmetry boundary conditions on either of these surfaces to make it essentially 2D.

For the solid portion of the geometry, I apply a fixed boundary condition at the top of the leaflet and a fluid structure interface condition where it contacts the fluid to receive force data.

For the fluid geometry, I apply a small pressure (0.05 Pa) for 0.01s to the inlet and set the outlet at zero-pressure. I realize this pressure is low, but keep in mind it's a physiological material and will deform quickly under very small pressures. I am using the Spring/Laplace/Boundary Layer smoothing setting as well as the local cell remeshing tool. The mesh is a swept mesh one element thick (using coarse settings) with a triangular/tetrahedral mix. I realize this mesh is coarse, but the Reynolds numbers in these simulations are less than 1.

I've tried decreasing the time-step by an order of magnitude, but this seems to only exacerbate the problem and the solution crashes much more quickly due to negative volumes. I've even decreased the pressure and momentum relaxation parameters, but this doesn't help either.

Any suggestions/comments from people in the forum would be great appreciated. Please let me know if you'd like me to clarify any details.
jtwilson is offline   Reply With Quote

Old   June 2, 2015, 16:37
Default
  #2
Senior Member
 
Join Date: Apr 2009
Posts: 531
Rep Power: 20
stumpy is on a distinguished road
Local cell remeshing may not be doing anything here. If you have a 1 element thick swept mesh then that mean you have prism elements (tri face swept into a tri prism). Local cell remeshing only works on tet elements, so you would actually need the 2.5D remeshing method. The Fluent FSI training course on the ANSYS customer portal has a workshop that uses 2.5D remeshing.
In any case, I don't think that's the main problem. Probably the coupling is unstable and Solution Stabilization is needed. There's a solution posted here:
https://support.ansys.com/AnsysCusto...upling/2022119
stumpy is offline   Reply With Quote

Old   June 2, 2015, 16:40
Default
  #3
New Member
 
Join Date: Apr 2013
Posts: 6
Rep Power: 12
jtwilson is on a distinguished road
Hi thanks so much for the response. I'll look at trying 2.5D remeshing, however, I actually ended up having to reduce my under-relaxation term in one of the data transfers - the solution now converges.
jtwilson is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Is Playstation 3 cluster suitable for CFD work hsieh OpenFOAM 9 August 16, 2015 15:53
Gate valve flow simulations... nikesh FloEFD, FloWorks & FloTHERM 5 January 28, 2014 02:31
Valve simulation with spring - FSI? Help! farianka CFX 1 April 17, 2011 19:04
Simulation of air flow inside valve - FSI? Help! farianka Main CFD Forum 0 April 17, 2011 17:30
Ansys FSI and CFX (valve simulation) farianka ANSYS 0 April 17, 2011 17:20


All times are GMT -4. The time now is 05:16.