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

CFD of three phase bubble column

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   April 6, 2004, 03:08
Default CFD of three phase bubble column
  #1
ANIL
Guest
 
Posts: n/a
I'm M.Anil, doing M.Tech Chemical, IIT, Roorkee, India.I'm new is to field of CFD, I'm doing my thesis on CFD of three phase bubble column using CFX-5.6, I'm getting satisfactory results for velocity profile and volume fraction but pressure profile is coming wrong ie; pressure at inlet is lower than pressure at outlet. my system is air ,water and glass beads. At inlet boundary ie sparger I'm specifying velocities and at outlet boundary I'm specifying as degassing condition. I'm also considering buoyancy in vertical direction as –g (-9.81 m/s2). So can anyone suggest my what is the problem in this ? My email id is mik_anil@rediffmail.com

M.Anil
  Reply With Quote

Old   April 6, 2004, 11:03
Default Re: CFD of three phase bubble column
  #2
BAK_FLOW
Guest
 
Posts: n/a
Dear Anil,

the solution in CFX-5 (and most other CFD codes) uses a reduced pressure ie P* = P_thermodynamic - P_hydrostatic

The P_hydrostatic is the hydrostatic pressure that would occur if the fluid were all at density rho_ref.

This is useful numerically since the pressure and hydrostatic terms could nearly cancel themselves and it is only the net effect that acts on the fluid. In finite precision of a computer this can lead to round-off problems. This is also useful in specifying pressure boundary conditions because the hydrostatic contribution does not need to be added and constant P* at an outlet is a good approximation.

So what you need to do is either specify rho_ref = 0.0 or take the resulting pressure field (P*) and add the hydrostatic contribution back on in post-processing.

If you are a member of the cfx-community there is a useful tech tip on this entitiled "Setting boundary conditions at openings in buoyant flows with stagnant atmospheres"

Regards,

Bak_Flow
  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
bubble column ken FLUENT 1 June 30, 2013 02:18
Experts in Simulating BUbble Column Reactors aliyah Main CFD Forum 7 June 19, 2012 03:38
bubble rising in a column swamysrikanth Main CFD Forum 2 September 27, 2010 09:59
CFD and Three Phase Fluidization shashidhar C CFX 0 September 15, 2005 10:19
public CFD Code development Heinz Wilkening Main CFD Forum 38 March 5, 1999 12:44


All times are GMT -4. The time now is 03:46.