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

problem in solving fsi simulation

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   July 9, 2009, 05:31
Default problem in solving fsi simulation
  #1
New Member
 
siavash ghassemi
Join Date: Jul 2009
Posts: 11
Rep Power: 17
siavash is on a distinguished road
Hello every one,
in a FSI problem a solid circle moves in water.i use ansys & cfx11.0 for this simulation but it stops with errors.(negative element volume & folded mesh).i change the size of meshes and velocities many times but it doesn't work.a simple image is attached.
thanks,
Attached Files
File Type: zip 2.zip (23.0 KB, 33 views)
siavash is offline   Reply With Quote

Old   July 9, 2009, 05:53
Default
  #2
Senior Member
 
ckleanth's Avatar
 
George
Join Date: Mar 2009
Location: Birmingham, UK
Posts: 257
Rep Power: 18
ckleanth is on a distinguished road
what type of mesh do you use? - I wouldn't be surprised if you used tetra with cfx mesh as its very easy to distort your mesh and have the problems you just mentioned.

if this is the case the solution is:
a) use a different meshing tool to create a purely hexa mesh if your simulation is 2d as in your picture.
b) if the above is not available create a better mesh around the circle stop, remesh and restart your simulation depending of the movement of the mesh in your problem.
c) upgrade in v12 as the meshing tools are better and a lot more functions are available to use in cfx
__________________
Top 4 tips
1. Knowledge is everything and Ignorance is dangerous.
2. Understand your limitations and try to eliminate them.
3. Get yerself a bike and hoon the chuffer. You will soon learn why dogs like to hang their heads out the car window.
4. Please before asking any questions on how to run simulations in CFX, go though all the tutorials
ckleanth is offline   Reply With Quote

Old   July 9, 2009, 10:11
Default
  #3
Senior Member
 
Michael P. Owen
Join Date: Mar 2009
Posts: 196
Rep Power: 17
michael_owen is on a distinguished road
Is the cylinder constrained from touching the wall in some fashion (like spring mounting it)? Unless it is, the code will inevitably crash when the cylinder approaches the wall.

Other than that, the two main things in problems like this are to reduce the timestep and increase the number of convergence iterations for the mesh displacement, on the equation class settings tab of the Solver Controls from the default 5.

Another problem you could run into, even if the cylinder cannot touch the walls, is that if it moves a significant distance down the channel, it can stretch the elements until they fold because of the curvature of the front of the cylinder. A technique that I would use here would be to cut out a section of the channel around the cylinder, and move the ENTIRE block parallel to the channel, and the cylinder within the block transverse to the channel. Obviously this would require some advanced CEL.

Or switch to R12.
michael_owen is offline   Reply With Quote

Old   July 9, 2009, 19:35
Default
  #4
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,862
Rep Power: 144
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
Hi,

This should be fairly easy in the immersed solid feature and 6DOF solver in V12. I would recommend you upgrade to V12, it will be much easier.

Glenn Horrocks
ghorrocks is offline   Reply With Quote

Old   July 10, 2009, 12:54
Default
  #5
New Member
 
siavash ghassemi
Join Date: Jul 2009
Posts: 11
Rep Power: 17
siavash is on a distinguished road
as you wrote i used tetra mesh!
if i create hexa mesh can i generate a "gtm" file?
thanks for your answer.
siavash is offline   Reply With Quote

Old   July 10, 2009, 12:59
Default
  #6
New Member
 
siavash ghassemi
Join Date: Jul 2009
Posts: 11
Rep Power: 17
siavash is on a distinguished road
thanks for your answer.
siavash 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
SimpleFoam k and epsilon bounded nedved OpenFOAM Running, Solving & CFD 1 November 25, 2008 21:21
On the damBreak4phaseFine cases paean OpenFOAM Running, Solving & CFD 0 November 14, 2008 22:14
Parallel rasInterFoam openfoam_user OpenFOAM Running, Solving & CFD 4 November 1, 2008 05:14
Differences between serial and parallel runs carsten OpenFOAM Bugs 11 September 12, 2008 12:16
Problem in solving combustion simulation Ramesh FLUENT 0 June 2, 2006 13:21


All times are GMT -4. The time now is 12:59.