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

FSI with Ansys CFX: Error --> Excessive distortion of Element

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

Sponsored Links

Reply
 
LinkBack Thread Tools Display Modes
Old   October 1, 2014, 16:14
Default FSI with Ansys CFX: Error --> Excessive distortion of Element
  #1
New Member
 
Philipp
Join Date: Jul 2014
Posts: 6
Rep Power: 5
newuser! is on a distinguished road
Sponsored Links
Hi there,

my model consists of a straight, waterfilled pipe. One end of the pipe is closed by a thin rubber membrane, where the fluid interacts with the structure. The other end is open and "loaded" by a pressure of 1000Pa.
The aim is to calculate the transient solution of the vibration of the membrane, e.g. at the centernode of the structure.

Performing a multifield Ansys-CFX simulation, I had a "kick-off" model with coarse mesh, without partitioned bodies, .... . There, the FSI worked well and I got a physical solution.

Now, I refined the mesh, partitioned the fluid and structure bodies and tried again to perform the simulation, but it failed, see files attached.

1) As I guess, the simulation aborts since structure elements are distorted. Am I right or is it the CFX-part that fails?

2) Can anyone give me advice what could be the reason for these problems? I read already the thread " FSI and size of time-steps" but I could not get rid of the problem.

Best regards
Philipp

ANSYS.txt

Fluid_001.txt
newuser! is offline   Reply With Quote
Sponsored Links

Old   October 10, 2014, 04:13
Default
  #2
Senior Member
 
Matthias Voß
Join Date: Mar 2009
Location: Berlin, Germany
Posts: 448
Rep Power: 13
mvoss is on a distinguished road
The Ansys output shows a relatively high z-force after the very first time step (5e-4) you should check your initial fields.The error is due to the Ansys part, since CFX isn´t starting at all.
mvoss is offline   Reply With Quote

Old   October 21, 2014, 16:43
Default
  #3
New Member
 
Philipp
Join Date: Jul 2014
Posts: 6
Rep Power: 5
newuser! is on a distinguished road
Dear Mr. Voss,

thank you very much for this hint. I applied the pressure of 1000Pa instantaneous and used an incompressible fluid at the same time....
Maybe that was the reason for failure.

Using a slight ramp for pressure load (also reduced to 250Pa) and a slightly compressible water, I still get high values of Fz, but the simulation does not abort.
Do you have an explanation for this?
The pressure acts normal to the xy-Plane....

Last edited by newuser!; October 21, 2014 at 16:57. Reason: added comments
newuser! is offline   Reply With Quote

Old   October 21, 2014, 17:18
Default file
  #4
New Member
 
Philipp
Join Date: Jul 2014
Posts: 6
Rep Power: 5
newuser! is on a distinguished road
I appended the Ansys-out-file....
Attached Files
File Type: zip ansys.zip (92.8 KB, 7 views)
newuser! is offline   Reply With Quote

Old   February 2, 2015, 03:02
Default
  #5
New Member
 
Join Date: May 2013
Posts: 4
Rep Power: 6
zzura is on a distinguished road
may i know how you ramp the pressure
zzura is offline   Reply With Quote

Old   February 2, 2015, 05:09
Default
  #6
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 13,647
Rep Power: 105
ghorrocks is a jewel in the roughghorrocks is a jewel in the roughghorrocks is a jewel in the rough
This is basic stuff which is covered in the CFX tutorials. Have you looked at them?
ghorrocks is offline   Reply With Quote

Old   September 8, 2016, 05:17
Default
  #7
New Member
 
王琼瑶
Join Date: Apr 2014
Posts: 17
Rep Power: 5
hellowqy is on a distinguished road
Quote:
Originally Posted by newuser! View Post
Dear Mr. Voss,

thank you very much for this hint. I applied the pressure of 1000Pa instantaneous and used an incompressible fluid at the same time....
Maybe that was the reason for failure.

Using a slight ramp for pressure load (also reduced to 250Pa) and a slightly compressible water, I still get high values of Fz, but the simulation does not abort.
Do you have an explanation for this?
The pressure acts normal to the xy-Plane....
Dear Mr. Nnewuser
Thank you very much for you information. I recently also do the FSI simulation (the interaction between water and membrane), which is very similar with your case. Here I have some questions: 1. Why my simulation stops at the beginning even though I set the load to be zero. The error report said that there some elements of highly distortion. I improved the element quality and decreased the time step, still the same results. someone said my be the rubber material for the membrane is the problem. the data for the rubber material is density=1100kg*m^-3,young's modulus=1e7 Pa
poission's ratio=0.45.
2. How to make the liquid(like water) to be incompressible.
thanks a lot!
hellowqy is offline   Reply With Quote

Reply

Thread Tools
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 On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Compressible Flow in Ansys CFX bcheruk CFX 15 July 6, 2017 06:30
how to reatart a ansys cfx FSI? cyy CFX 0 July 3, 2012 22:17
Fsi ansys cfx? Mostafa.T CFX 5 March 31, 2010 10:16
CFX bought by Ansys - good or bad?! Pete CFX 38 February 21, 2003 08:34
ANSYS to acquire CFX Fred CD-adapco 0 February 18, 2003 22:03

Sponsored Links


All times are GMT -4. The time now is 03:25.