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

Udf about the distribution of the diameter

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

Reply
 
LinkBack Thread Tools Display Modes
Old   April 1, 2005, 21:09
Default Udf about the distribution of the diameter
  #1
as
Guest
 
Posts: n/a
My problem is about writing UDF program. I want use Mixture model to simulate two phase flow. I want to write a UDF about the distribution of the diameter of solid particles In my flow ,about 10 percent(10%) of the solid particles is 20 micron. about 90 percent(90%£© of the solid particles is 50 micron¡£
  Reply With Quote

Old   April 1, 2005, 21:10
Default Re: Udf about the distribution of the diameter
  #2
as
Guest
 
Posts: n/a
Can anyone help me about the UDF .Thank you
  Reply With Quote

Old   April 2, 2005, 14:55
Default Re: Udf about the distribution of the diameter
  #3
ap
Guest
 
Posts: n/a
I'm not sure it's possible to do this. Check the manual.

Regards, ap
  Reply With Quote

Old   April 2, 2005, 20:10
Default Re: Udf about the distribution of the diameter
  #4
as
Guest
 
Posts: n/a
Thank you for you response !I can not find any example in the manual ,I want to know if the udf can solve this problem
  Reply With Quote

Old   April 3, 2005, 00:44
Default Re: Udf about the distribution of the diameter
  #5
pUl|
Guest
 
Posts: n/a
I do not know if the following makes any sense at all, but I do know that fluent lets you do this without any errors or warnings which makes it even dangerous to use

Define the 'Primary phase' as usual. Next define 2 'Secondary phases'. Let both the secondary phases represent the same dispersed material. Define different diameters for both the secondary phases. Under "Interaction" disable any interaction between either secondary phase (i.e. drag). Carry on with the problem definition as usual. Once the solution has converged, define a "Custom field function" that equals (1 - volume fraction of the continuous phase) which will now give you the volume fraction of the dispersed phase. One of the things to think about is defining inlet velocities and volume fraction guesses for the dispersed phase. Whatever you do, you need to ensure that the total mass flow rate of the dispersed phase matches with what you would have had, if you introduced a mono-dispersed dispersed phase. This would seem like simulating a size distribution without breakup or coalescence, but I stll have my doubts. On second thoughts, it does seem to make no sense, so please use at your own risk!
  Reply With Quote

Old   April 3, 2005, 10:15
Default Re: Udf about the distribution of the diameter
  #6
ap
Guest
 
Posts: n/a
Yes, this is a tecnique used to simulate a size distribution for example in gas-solid flows.

In this case it seems ok, but if you have a spread size distribution it's not convenient because you have to use too many secondary phases, increasing the computational time too much.

One question: why do you have to disable the interaction between secondary phases? You should just choose the proper drag correlation.

Regards, ap
  Reply With Quote

Old   April 3, 2005, 16:33
Default Re: Udf about the distribution of the diameter
  #7
pUl|
Guest
 
Posts: n/a
Wow ap, thanks for your reply. I never knew whether this method was accepted for use.

The reason for disabling the interaction between the two secondary phases (same dispersed material) is that I find it rather unreasonable to believe that two gas bubbles for instance can have a 'drag' kind of interaction between each other when the possibilities of coalescence seem much more possible.

Perhaps you could shed more light on this.

Best Regards,

Srinath Madhavan
  Reply With Quote

Old   April 3, 2005, 18:36
Default Re: Udf about the distribution of the diameter
  #8
ap
Guest
 
Posts: n/a
I don't know that much about bubbles. I only saw this tecnique applied to fluidised beds.

Just look for more information in the literature. For example, look on the Elsevier journals, like Chemical Engineering Journal or so.

Regards, 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
bubble diameter distribution emrahdeniz FLUENT 0 September 27, 2010 08:03
UDF of linear distribution of temperature in a 2D tank arailos Fluent UDF and Scheme Programming 1 August 19, 2010 15:14
UDF for bubble diameter in two phases, help!! edgar h FLUENT 0 June 19, 2008 21:37
udf for drop size distribution Rashmi FLUENT 6 December 12, 2005 00:09
DPM diameter mass distribution Wouter FLUENT 4 November 30, 2005 04:36


All times are GMT -4. The time now is 06:59.