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

traction free bc

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

Reply
 
LinkBack Thread Tools Display Modes
Old   November 25, 2010, 14:36
Default traction free bc
  #1
Senior Member
 
ali
Join Date: Oct 2009
Posts: 157
Rep Power: 7
alinik is on a distinguished road
Hi everyone

Does anybody know haw can I introduce "traction free" BC at the outlet of my domain in CFX?

Regards
alinik is offline   Reply With Quote

Old   November 25, 2010, 17:36
Default
  #2
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,794
Rep Power: 84
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
What is a traction free BC?
ghorrocks is offline   Reply With Quote

Old   November 25, 2010, 23:18
Default
  #3
Senior Member
 
ali
Join Date: Oct 2009
Posts: 157
Rep Power: 7
alinik is on a distinguished road
this relation is called "traction"

T=-pI+2*mu*D,D=0.5*[grad(u)+grad(u)^T]

whenever it equals to zero, there is no traction or we can say it is traction free
alinik is offline   Reply With Quote

Old   November 25, 2010, 23:18
Default
  #4
Senior Member
 
ali
Join Date: Oct 2009
Posts: 157
Rep Power: 7
alinik is on a distinguished road
by the way "mu" is viscosity of the fluid
alinik is offline   Reply With Quote

Old   November 27, 2010, 05:34
Default
  #5
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,794
Rep Power: 84
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
I assume u is the velocity field. What is p and I?

Can you explain what is the physical significance of this?
ghorrocks is offline   Reply With Quote

Old   November 27, 2010, 07:03
Default
  #6
Senior Member
 
ali
Join Date: Oct 2009
Posts: 157
Rep Power: 7
alinik is on a distinguished road
P is pressure and I is the Identical matrix. it is said that this kind of bc does not affect the upstream flow conditions significantly
alinik is offline   Reply With Quote

Old   November 27, 2010, 08:02
Default
  #7
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,794
Rep Power: 84
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
I see.

You may be able to do it as a CEL function on an outlet boundary condition with a CEL specified velocity or pressure, but you probably have to implement it in fortran.
ghorrocks 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
Can Flow-3D plot the free surface area in Iso-surface or colour variable? therockyy FLOW-3D 1 June 20, 2010 19:36
What does "traction free" mean? Yang Main CFD Forum 12 November 9, 2009 07:43
free RANS code with free surface ability Lou jing Main CFD Forum 1 July 11, 2003 14:43
CFX 4.4 New free surface option Viatcheslav Anissimov CFX 0 April 3, 2002 06:27
Variable Density - Free Surface with FIDAP Vitaliy Pavlyk FLUENT 7 May 2, 2000 15:56


All times are GMT -4. The time now is 21:27.