CFD Online Logo CFD Online URL
Home > Forums > FLUENT

How to choose a good model for multiphasis flow ?

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

LinkBack Thread Tools Display Modes
Old   April 15, 2008, 03:40
Default How to choose a good model for multiphasis flow ?
Posts: n/a

i wish to simulate a truck in a multiphasis flow with a 2D geometry. the principal phase is air and the other one is water liquid. the multophase model is mixture. the problem with this modelisation is that the turbulent viscosity increase enormously. indeed, there is a swirl which is created by the truck. residuals converge for very little water particles ( average 1e-5m). however, residuals become "crazy" for larger water particles. i have modified under-relaxation number but the calculus is diverging. i have tested this model with k-espilon and k-omega viscous model. all of them diverge.

some one has ever done a simulation like mine ?

do you have any idea about dirverging reasons ?

thank you for your answers.

  Reply With Quote

Old   April 18, 2008, 12:52
Default Re: How to choose a good model for multiphasis flo
Posts: n/a
you may try transient run with large time step instead od steady state. Hope this may give better results.
  Reply With Quote

Old   April 21, 2008, 02:12
Default Re: How to choose a good model for multiphasis flo
Posts: n/a
time step increasing doesn't any result. the matter of this model is the water-liquid drop size. indeed when i use a diameter inferior to 10^-5 m, residuals converge. however for a 10^-3 m drop the model is totally instable. it's due to the increasing of the turbulent viscosity. this message appears during calculation " turbulent viscosity limited to viscosity ratio of 1.000000e+05 in 202602 cells". i ever try to reduce the under-relaxation number for viscosity, but it does not work. i submit this problem to fluent-support, but they do not give me an answer. they probably hope i will forget.
  Reply With Quote


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
Which turbulence model to choose? Si Del FLUENT 3 February 8, 2008 05:24
How to choose proper reaction model? jisel FLUENT 0 April 18, 2006 11:11
Which model should I choose when I don't known the Jeff FLUENT 0 June 19, 2005 10:59
what boundary do I choose for the counter-flow ? Gali FLUENT 0 October 20, 2004 05:44
How to choose the buoyancy model? ben Phoenics 2 April 8, 2002 04:04

All times are GMT -4. The time now is 02:13.