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

Recent updates done to libforces

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   May 28, 2010, 09:42
Default Recent updates done to libforces
  #1
Senior Member
 
Pierre-Olivier Dallaire
Join Date: Mar 2009
Location: Montreal, Quebec, Canada
Posts: 192
Rep Power: 17
podallaire is on a distinguished road
Good day,

I'm very impressed with the new updates that were done in libforces / the
ability to use constraints and restraints is very interesting.

I just have a simple suggestion regarding the springs. With the report option "on",
the spring lengths and angles are displayed. However, I understand that the
magnitude is returned, meaning that the values are always > 0. It would be a
good thing if the "sign" would be included as well / it makes it easier to track
the exact position in time of the rigid body.

Regards,

PO
podallaire is offline   Reply With Quote

Old   May 31, 2010, 07:47
Default
  #2
New Member
 
Graham Macpherson
Join Date: Mar 2009
Posts: 8
Rep Power: 17
gmacpherson is on a distinguished road
Hello,

Quote:
I'm very impressed with the new updates that were done in libforces / the
ability to use constraints and restraints is very interesting.
Thanks.

Quote:
I just have a simple suggestion regarding the springs. With the report option "on",
the spring lengths and angles are displayed. However, I understand that the
magnitude is returned, meaning that the values are always > 0. It would be a
good thing if the "sign" would be included as well / it makes it easier to track
the exact position in time of the rigid body.
I have pushed this to 1.6.x.

What to do with the sign of the angle was unambiguous, but linear springs can start with zero length and move in any direction, so the concept of a sign for their displacement is not always clear. I added reporting of the vector from the anchor to the instantaneous attachment point on the body.

Graham
gmacpherson is offline   Reply With Quote

Old   May 31, 2010, 11:54
Default
  #3
Senior Member
 
Pierre-Olivier Dallaire
Join Date: Mar 2009
Location: Montreal, Quebec, Canada
Posts: 192
Rep Power: 17
podallaire is on a distinguished road
Thanks for the changes / will give it a try.

Another question -> did you try to run a case with single cpu for some time
and then, decompose the latest time step for a multi-cpu run ? I most be
missing something because I just cannot run multi-cpu if I try that. I guess I
need to move the latest time/polyMesh/points file in constant/polyMesh before
decomposing or something like that ... Not sure what is the best practice for
this.

Regards,

PO
podallaire is offline   Reply With Quote

Old   June 2, 2010, 06:10
Default
  #4
New Member
 
Graham Macpherson
Join Date: Mar 2009
Posts: 8
Rep Power: 17
gmacpherson is on a distinguished road
There are some issues to do with decomposing moving mesh cases in 1.6.x that have been fixed in our internal development version.

For the moment, best practice would be to decompose the case at the start and do everything in parallel.

Graham
gmacpherson is offline   Reply With Quote

Old   June 3, 2010, 09:20
Default
  #5
Senior Member
 
Pierre-Olivier Dallaire
Join Date: Mar 2009
Location: Montreal, Quebec, Canada
Posts: 192
Rep Power: 17
podallaire is on a distinguished road
Ok, thanks Graham
podallaire is offline   Reply With Quote

Old   June 10, 2010, 11:33
Default
  #6
Senior Member
 
Pierre-Olivier Dallaire
Join Date: Mar 2009
Location: Montreal, Quebec, Canada
Posts: 192
Rep Power: 17
podallaire is on a distinguished road
Good day Graham,

I have another question related to the definition of the damping for the
restraints. Can you confirm that the damping input is in fact the damping ratio,
in percentage, meaning that an input of 0.5 means 0.5% damping ratio (or
0.005). Also, can you confirm that this works for both axial spring and vertical
spring / I'm facing some discrepancies in my decay tests.

Regards,

PO
podallaire is offline   Reply With Quote

Old   June 10, 2010, 11:51
Default
  #7
New Member
 
Graham Macpherson
Join Date: Mar 2009
Posts: 8
Rep Power: 17
gmacpherson is on a distinguished road
It is not a damping ratio, it is a damping coefficient.

For the definition see linearSpring.H

Code:
//- Damping coefficient (Ns/m)
scalar damping_;
and .C

Code:
restraintForce = -stiffness_*(magR - restLength_)*r - damping_*(r & v)*r;
Graham
gmacpherson is offline   Reply With Quote

Old   October 6, 2010, 20:13
Default Some results
  #8
Senior Member
 
lakeat's Avatar
 
Daniel WEI (老魏)
Join Date: Mar 2009
Location: Beijing, China
Posts: 689
Blog Entries: 9
Rep Power: 21
lakeat is on a distinguished road
Send a message via Skype™ to lakeat
Hi I made some fsi videos using pimpleDyMFoam, but quite rudiment, It is a wind tunnel case. I found the new patch is very capable for some rigid body movement simulation, Good.


Video Link
__________________
~
Daniel WEI
-------------
Boeing Research & Technology - China
Beijing, China
Email
lakeat 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
Paper Request (recent years, 2003-2005) rt Main CFD Forum 1 February 27, 2007 10:35
Share updates for star-cd v3.26 or v3.24 denizen Siemens 10 December 16, 2006 16:30
most recent research area in CFD omr Main CFD Forum 0 March 11, 2005 03:33
Gambit on RedHat 7.3 with recent nvidia driver Jonas Larsson FLUENT 4 May 6, 2003 11:46
Recent Flame-Wars Jonas Larsson Main CFD Forum 12 October 26, 2001 17:47


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