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

piston-cylinder UDF

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

Reply
 
LinkBack Thread Tools Display Modes
Old   September 16, 2008, 02:19
Default piston-cylinder UDF
  #1
carno
Guest
 
Posts: n/a
Hi,

I am trying to move the piston in a 2D piston cylinder arrangement with CG_MOTION macro. Piston is moving correctly but the mesh along the cylinder is not changing and the end point of the cylinder is remaining at its original position and creating problem of mesh distortion.

1. Initial position: arrangement look like a rectangle with piston at BDC. 2. After some time the piston moves up and arrangement look like a rectangle with bottom end open and piston at some position in the open rectangle. (cylinder side lengths remain same). This is the problem and the run comes out with negative volume error.

How to resolve this problem?

Thanks
  Reply With Quote

Old   September 16, 2008, 08:04
Default Re: piston-cylinder UDF
  #2
doki
Guest
 
Posts: n/a
I'm wonder if I've understood the problem correctly, but the thing is you have to define the piston walls as All of your bottom edge. Also, you probably should define the cylinder liner as "deforming" in fluent. the negative volume is probably because of a crevice-like portion between the piston and cylinder liner.
  Reply With Quote

Old   September 17, 2008, 00:30
Default Re: piston-cylinder UDF
  #3
carno
Guest
 
Posts: n/a
Thanks Doki. After defining the deforming cylinder wall problem got solved.
  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
help to simulate 4-stroke piston cylinder san CD-adapco 2 September 29, 2006 13:37
CFD Work on 4-stroke piston cylinder san FLUENT 0 September 20, 2006 13:27
tutorial for 3D CYLINDER-PISTON ARRANGEMENT sachin bhalerao FLUENT 0 February 28, 2006 04:05
piston/cylinder leak Elsayed M Main CFD Forum 1 September 1, 2004 11:21
Mesh for Cylinder-Piston? Serkan Cetin Main CFD Forum 3 December 4, 2002 12:44


All times are GMT -4. The time now is 06:00.