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

measuring gas holdup

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

Like Tree1Likes
  • 1 Post By hemenkhaled

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   February 15, 2012, 14:48
Question measuring gas holdup
  #1
New Member
 
hemen khaled
Join Date: Jan 2012
Posts: 4
Rep Power: 14
hemenkhaled is on a distinguished road
I want to simulate a bubble column in cfx. How can I measure gas holdup in cfx post?please help me.
thanks.
saeidmahdavi likes this.
hemenkhaled is offline   Reply With Quote

Old   June 16, 2012, 18:34
Default
  #2
New Member
 
Join Date: Mar 2009
Location: Jaltipan, Veracruz,Mexico
Posts: 5
Rep Power: 16
zolrack is on a distinguished road
very simple. you must to monitoring the gas volume fraction. If you are modelling air -water, the air is a dispersed phase. so you shold measure the air volume fraction. I suggest you measure time average gas holdup
zolrack is offline   Reply With Quote

Old   April 30, 2015, 00:44
Default
  #3
New Member
 
Rahul omar
Join Date: Aug 2013
Posts: 12
Rep Power: 12
omar.rahul is on a distinguished road
how to measure the time average gas holdup.
omar.rahul is offline   Reply With Quote

Old   April 30, 2015, 02:13
Default
  #4
New Member
 
Join Date: Mar 2009
Location: Jaltipan, Veracruz,Mexico
Posts: 5
Rep Power: 16
zolrack is on a distinguished road
you need to créate a transient simulation and add in the output a aritmetic average to account for thr "Time or Trnavg" for each timestep
zolrack is offline   Reply With Quote

Old   April 30, 2015, 03:31
Default
  #5
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,655
Rep Power: 143
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
There is a neat way of doing this which does not require a transient simulation . You create an additional variable with units of time. You make the variable have a convection equation (but not diffusion), and start at the inlet with time = 0. You then put a source term on additional variable on the entire domain of 1 [1/s].

This creates an additional variable which moves around with the fluid and the source term makes it increment by time. By the time it reaches the outlet it has incremented to the residence time.

(I may have details of the implementation wrong, hopefully somebody will correct me if this is the case. But I know the approach works.)
ghorrocks is offline   Reply With Quote

Old   April 30, 2015, 03:36
Default
  #6
New Member
 
Join Date: Mar 2009
Location: Jaltipan, Veracruz,Mexico
Posts: 5
Rep Power: 16
zolrack is on a distinguished road
Hi, I think the additional variable helps if you want to track the particles as a residence time distribution, but if you need to know the "gas volumen fraction(time averaged) I suggest create TRNAVG variables in the output or create a PERL routine instead automatic aritmetic average in each timesteps.....regards
zolrack is offline   Reply With Quote

Old   January 1, 2018, 10:15
Default Air-water bubble column
  #7
New Member
 
Ritesh
Join Date: Jul 2017
Location: India
Posts: 7
Rep Power: 8
ritesh.prakash is on a distinguished road
How to ensure the accurate time average volume fraction in an air-water bubble column. I have monitored the volume weighted average of gas fraction and after the transient run of 60 seconds still the volume fraction is increasing. Please guide me, up to how much time I should run the simulation and how to ensure the converged volume weighted average of the gas fraction?
ritesh.prakash is offline   Reply With Quote

Old   January 1, 2018, 18:07
Default
  #8
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,655
Rep Power: 143
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
Why don't you just keep running the simulation and find out?
ghorrocks 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
mass flow in is not equal to mass flow out saii CFX 12 March 19, 2018 06:21
Constant velocity of the material Sas CFX 15 July 13, 2010 09:56
the profile of gas holdup CHAKER FLUENT 0 April 4, 2009 15:06
average gas holdup monitoring John CFX 1 August 30, 2005 22:44
Gas pressure question Dan Moskal Main CFD Forum 0 October 24, 2002 23:02


All times are GMT -4. The time now is 07:38.