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

Piston stroke cutoff

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

Reply
 
LinkBack Thread Tools Display Modes
Old   March 3, 2010, 10:00
Question Piston stroke cutoff
  #1
New Member
 
Chester
Join Date: Feb 2010
Posts: 24
Rep Power: 7
ChesterP is on a distinguished road
Dear all,

I can read the following in the user's guide about the piston stroke cutoff :

"... you need to specify the dynamic layering zone adjacent to the piston
surface to move with the piston until some specified distance from the TDC position. Beyond this cutoff distance, the motion of the layering zone is stopped and the piston wall is allowed to continue to the BDC position."

But it is not clear how to specify the layering motion (first rigid and then deforming). Do I have to write an UDF or create an event? My geometry was mesh in ICEM CFD with piston at TDC. My case is 3D and I have specified the motion of the piston head to rigid body with the built-in function "piston-full".

Thanks in advance,

Chester
ChesterP is offline   Reply With Quote

Old   March 7, 2010, 12:20
Default
  #2
New Member
 
Chester
Join Date: Feb 2010
Posts: 24
Rep Power: 7
ChesterP is on a distinguished road
Ok the solution is to use the built-in UDF **piston-limit** for the layering and **piston-full** for the piston head.
ChesterP is offline   Reply With Quote

Old   March 28, 2010, 02:00
Default
  #3
Member
 
李逾
Join Date: Mar 2010
Posts: 65
Rep Power: 7
yubaibai88 is on a distinguished road
Quote:
Originally Posted by ChesterP View Post
Ok the solution is to use the built-in UDF **piston-limit** for the layering and **piston-full** for the piston head.
so what does fluent do when runing with **piston-limit** or **piston-full**.
thanks
yubaibai88 is offline   Reply With Quote

Old   March 29, 2010, 17:22
Default
  #4
New Member
 
Chester
Join Date: Feb 2010
Posts: 24
Rep Power: 7
ChesterP is on a distinguished road
Quote:
Originally Posted by yubaibai88 View Post
so what does fluent do when runing with **piston-limit** or **piston-full**.
thanks
Hi,

**piston-limit** makes the body moves from TDC until the cut-off distance that you defined.
**piston-full** makes the body moves from TDC to BDC.

Hope it helps
ChesterP is offline   Reply With Quote

Old   March 31, 2010, 23:33
Default
  #5
Member
 
李逾
Join Date: Mar 2010
Posts: 65
Rep Power: 7
yubaibai88 is on a distinguished road
hi
'cut off' is still the problem which I don't know until now,what does it mean in a piston moving process and what effect does it have during the moving
yubaibai88 is offline   Reply With Quote

Old   April 1, 2010, 03:57
Default
  #6
New Member
 
Chester
Join Date: Feb 2010
Posts: 24
Rep Power: 7
ChesterP is on a distinguished road
Ok the cut-off distance is the distance until which the layering part of your mesh will move as a rigid body.It will then stop moving when reaching that distance but the piston head will continue to move until it will reach BDC and as a consequence the layering process will begin from that cutoff distance.

You need that in order to create a space in the upper part of your cylinder that is meshed with tetrahedra and that is big enough (greater than you dead volume) to ensure that your valves can fully move in that zone and that the smoothing and remeshing process can happen. In other words your valves cannot touch your HEX layer.

Is that clear enough?

Have a nice day
ChesterP is offline   Reply With Quote

Old   April 1, 2010, 10:29
Default
  #7
Member
 
李逾
Join Date: Mar 2010
Posts: 65
Rep Power: 7
yubaibai88 is on a distinguished road
thank you very much!
finally can I understand it until you describe!
yubaibai88 is offline   Reply With Quote

Old   April 1, 2010, 22:58
Default nice explanation
  #8
New Member
 
sunqiang
Join Date: Nov 2009
Posts: 23
Rep Power: 7
matthewsun is on a distinguished road
I've been looking for the answer for days, it's really great to get it here,thanks
matthewsun is offline   Reply With Quote

Reply

Tags
dynamic, in-cylinder, layering, remeshing

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
Mesh Motion (Piston valve) AliAli CFX 0 October 10, 2009 10:55
No pressure increase with compressing piston Erik CD-adapco 0 December 23, 2008 05:51
how to replace piston head in the es-ice software Julian CD-adapco 1 December 20, 2007 01:18
Moving mesh - compression stroke ICE muhsin hanis FLUENT 0 April 12, 2007 09:57
compression stroke in piston engine Hassaneen CD-adapco 12 December 29, 2000 13:30


All times are GMT -4. The time now is 16:00.