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

Transient outlet boundary condition problem

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

Reply
 
LinkBack Thread Tools Display Modes
Old   December 7, 2009, 07:11
Default Transient outlet boundary condition problem
  #1
Member
 
James Willie
Join Date: Mar 2009
Posts: 71
Rep Power: 8
jwillie2000 is on a distinguished road
Hello Eveyone,

I am doing premixed combustion in a compressible transient flow simulation using CFX. I first had a converged steady state simulation before switching to unsteady. My trouble is, after some time, i am getting this message in the output file:

"
****** Notice ****** |
| A wall has been placed at portion(s) of an OUTLET |
| boundary condition (at 100.0% of the faces, 100.0% of the area) |
| to prevent fluid from flowing into the domain. |
| The boundary condition name is: out. |
| The fluid name is: Propane Air Mixture. |
| If this situation persists, consider switching |
| to an Opening type boundary condition instead.
"

The outlet boundary i used is "pressure outlet" and the and i have "velocity inlet" for the air and "mass flow inlet" for the fuel. Because the outlet is reflecting i think pressure waves could be moving in into the flow, which is what I would expect. But do I have to specify any other boundary in addition to just a "pressure outlet"?

Thanks!

Jimmy
jwillie2000 is offline   Reply With Quote

Old   December 7, 2009, 18:07
Default
  #2
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,800
Rep Power: 85
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
Whether this is a problem depends on your model. Do you need to have correct reverse flow? If so you need an opening. If it does not matter then stick with an outlet. Even better, move the boundary condition further away so it always has flow in one direction.
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
outlet boundary condition for compressor modeling siamak1424 FLUENT 3 August 8, 2009 05:55
Transient Inlet boundary condition - fully develop Omer CFX 3 November 28, 2006 17:22
Periodic flow boundary condition problem sudha FLUENT 3 April 28, 2004 08:40
UDF for transient boundary condition? Shankar FLUENT 1 November 22, 2003 09:10
a problem with Boundary condition M Rad Main CFD Forum 12 November 27, 1998 13:49


All times are GMT -4. The time now is 02:03.