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

mass balance problem in transient simulation

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

Reply
 
LinkBack Thread Tools Display Modes
Old   April 14, 2010, 20:24
Unhappy mass balance problem in transient simulation
  #1
New Member
 
Qi Nana
Join Date: Apr 2010
Posts: 4
Rep Power: 7
nana84 is on a distinguished road
Hi, I am Nana, a new one of CFX online, I have a problem when running the transient simulation in bubble column. The problem is when the first seconds (before bubble reach the liquid surface), there only bubbles in, but no bubbles out, then the gas phase mass is imbalance, and if the liquid phase should go out from the top? How to set the outlet boundary condition? Degassing or opening? The software I am using is CFX 12.0.
nana84 is offline   Reply With Quote

Old   April 15, 2010, 07:31
Default
  #2
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,929
Rep Power: 85
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
Quote:
Degassing or opening?
The difference between these boundaries is explained in the documentation. Which one is suitable for your application will depend on what you are trying to model.
ghorrocks is offline   Reply With Quote

Old   April 15, 2010, 19:53
Post mass balance problem in transient simulation
  #3
New Member
 
Qi Nana
Join Date: Apr 2010
Posts: 4
Rep Power: 7
nana84 is on a distinguished road
Thank you for reply.
I want to know if there is a notice "A wall has been placed at portion(s) of an OUTLET |
| boundary condition (at 99.8% of the faces, 99.8% of the area) |
| to prevent fluid from flowing into the domain. |
| The boundary condition name is: OUTLET. |
| The fluid name is: Air. |
| If this situation persists, consider switching |
| to an Opening type boundary condition instead." in the solver, then if I should change the degassing b.c. to opening b.c?

And I have another problem: using either degassing or opening b.c. in the three-phase flow transient simulation, the residual curve will be show a jump at the same timestep. Is the drag force improper or what is happening?

Thank you!
nana84 is offline   Reply With Quote

Reply

Tags
bubble column, cfx12.0, degassing, mass balance, opening

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
Problem with transient simulation (icoFoam) skabilan OpenFOAM Running, Solving & CFD 20 June 18, 2014 11:36
mass conservation problem with VOF model pat77 FLUENT 2 November 5, 2012 08:07
Star-CD transient simulation, problem of loss of mass kit STAR-CD 3 April 13, 2010 11:34
Mass conservation problem in mixing tank multiphase simulation rockewan FLUENT 0 April 6, 2010 12:34
Mass balance problem! JADG FLUENT 4 December 27, 2003 11:40


All times are GMT -4. The time now is 23:09.