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

particle size distribution

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

Reply
 
LinkBack Thread Tools Display Modes
Old   January 27, 2004, 12:47
Default particle size distribution
  #1
Bob
Guest
 
Posts: n/a
I would like to use the Eulerian model to model the separation of water and oil in a vessel. When setting the size of the oil droplet I can only set a constant droplet size. Is it possible to put in a size distribution for the secondary phase?
  Reply With Quote

Old   January 27, 2004, 15:53
Default Re: particle size distribution
  #2
ap
Guest
 
Posts: n/a
You should be able to define particle diameter as a function using UDF.

See: http://www.engr.subr.edu/Support/flu...153.htm#190982

Hi

ap
  Reply With Quote

Old   January 27, 2004, 23:48
Default Re: particle size distribution
  #3
Anton
Guest
 
Posts: n/a
From what I gather, you have to specify additional secondary phases for each additional particle size you want to model. This is one of the drawbacks of the Eulerian model. Each additional secondary phase means yet another momentum equation that has to be solved.

  Reply With Quote

Old   January 28, 2004, 05:37
Default Re: particle size distribution
  #4
thomas
Guest
 
Posts: n/a
Hi, According to what i know distribution size of particle occurs because of the break-up/coalescence. To set a diameter you can use the macro C_PHASE_DIAMETER(c,t). Acording to me this would be helpful olny if you have a simple correlation giving you your droplet diameter depending on the height, volume fraction or something else. Also by setting a secondary phase you consider that the number of droplet is the same in each phase. In fact you consider there is no transfer inbetween due to the break up coaslence phenomena. The correct theory of that is the 'population balance theory' (Not sure if it's the right translation in English thought). I do know this can be done by UDF. Some other CFD code release paper about that too. I dunno think it is yet available as a default option in Fluent. You should ask to your nearest Fluent distributor for this.

Hope this help. thomas
  Reply With Quote

Old   January 28, 2004, 15:48
Default Re: particle size distribution
  #5
ap
Guest
 
Posts: n/a
I agree with Thomas. A good approach to model your system (oil in water) should be the use of population balances to keep into account coalescence and break-up. However this is not implemented in FLUENT yet. I know of some work on bubble columns and boiling beds which uses this tecnique (See MFIX Open Citations - Chemistry at www.mfix.org),

The approach proposed by Anton (many secondary phases to reproduce a distribution) has been applied to simulate particle size distribution in gas-solid fluidized systems, obtaining good results using 3 or more phases to represent the solid powder. Anyway, considering your system, where coalescence is an essential phenomenon to be taken into account, this approch doens't seem a good idea.

Hi

ap
  Reply With Quote

Old   January 29, 2004, 07:11
Default Re: particle size distribution
  #6
Bob
Guest
 
Posts: n/a
Hi,

Thanks for all your suggestions. After speaking with Fluent it seems the only way to model this is to use Antons suggestion of having muliple phases of oil with differnt droplet sizes. This clearly has limitations on computer resources, but is currently the only way at the moment.

Thanks
  Reply With Quote

Old   January 29, 2004, 20:32
Default Re: particle size distribution
  #7
ap
Guest
 
Posts: n/a
Maybe FLUENT peple mean it's the only way if you don't want to implement population balances, which should be possible using UDF.

Hi

ap
  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
Superlinear speedup in OpenFOAM 13 msrinath80 OpenFOAM Running, Solving & CFD 18 March 3, 2015 06:36
critical error during installation of openfoam Fabio88 OpenFOAM Installation 21 June 2, 2010 03:01
OF 1.6 | Ubuntu 9.10 (64bit) | GLIBCXX_3.4.11 not found piprus OpenFOAM Installation 22 February 25, 2010 14:43
Phase locked average in run time panara OpenFOAM 2 February 20, 2008 15:37
fluent add additional zones for the mesh file SSL FLUENT 2 January 26, 2008 12:55


All times are GMT -4. The time now is 17:50.