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

steady or unsteady? (in dpm)

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

Reply
 
LinkBack Thread Tools Display Modes
Old   April 28, 2003, 03:49
Default steady or unsteady? (in dpm)
  #1
winnie
Guest
 
Posts: n/a
Hi, everyone

I would like to discuss the steady and unsteady particle Lagrangian discrete phase model with you.

In Fluent document, we can find the explaination of steady and unsteady model as follows:

The steady-particle Lagrangian discrete phase model is suited for flows in which particle streams are injected into a continuous phase flow with a well-defined entrance and exit condition.

The unsteady-particle discrete phase model, however, is capable of modeling continuous suspensions of particles.

In my opinion, whether we should use steady or unsteady model depends on the procedure of each model:

1) steady model: In each iteration, firstly the continuous phase flow field is solved and then based on it the particle streams with definite entrance and exit condition are created. Iteration goes on until both the continuous phase flow field and particle trajectory never change.

2)unsteady model: particle trajectory is calculated step by step; another word, after each time step, particle will be advanced to a new position. In each time step, the iteration between continuous phase and particle is going on. In each iteration, there are sub-iteration in the continuous phase per DPM iteration which is controled by the "number of continuous phase iteration per DPM iteration" in Discrete Phase Model panel.

From what I have discussed above, I find that a problem such as bubbly flow in a pipe can be solved by using both steady and unsteady model and the result of a steady one should be the same as the result of an unsteady one when the particle of the unsteady model has escaped from the exit.

I don't know if my understanding is right. Hope anyone who has experience in DPM can give me some suggestions.

Thank you very much for reading a so long message.

Regards

winnie
  Reply With Quote

Old   April 28, 2003, 11:30
Default Re: steady or unsteady? (in dpm)
  #2
phd_y2k2001
Guest
 
Posts: n/a
In the real life, there are few steady state particle flow.

Most unsteady cases become virtually steady if we can remove the same amount of particles from the domain by any means. Accumulation of particles in the domain will make the local density of the particles more than 10% and the DPM will no longer will be applicable.

Well, in case I am confusing you, I will stop here
  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
Unsteady DPM with steady solver elobb FLUENT 3 May 31, 2015 04:11
unsteady DPM and steady flow Mohsin FLUENT 6 October 9, 2014 05:30
Steady needs unsteady. nico Main CFD Forum 0 September 21, 2007 04:50
steady or unsteady DPM ??? Marina FLUENT 5 July 5, 2006 04:52
Turbulent: Steady or Unsteady: confusion prem FLUENT 0 March 30, 2006 10:40


All times are GMT -4. The time now is 06:17.