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

Singularity in two fluid model (Eulerian-Eulerian)

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

Reply
 
LinkBack Thread Tools Display Modes
Old   December 7, 2008, 03:01
Default Singularity in two fluid model (Eulerian-Eulerian)
  #1
Zak
Guest
 
Posts: n/a
In the Eulerian two-fluid model for two-phase flows, the standard formulation for the momentum equations becomes singular as the volume fractions tend to zero. Some papers suggest that resulting velocities can fluctuate widely in the regions where volume fractions tend to vanish.

How do you deal with the problem of singularity in your code?

Or could you give me some effective suggestions for the problem or references about Eulerian-Eulerian Model?

Thanks!
  Reply With Quote

Old   December 8, 2008, 02:39
Default Re: Singularity in two fluid model (Eulerian-Euler
  #2
vadim
Guest
 
Posts: n/a
single phase or decoupled phase formulation is an effective method, you can get idea from immersed bc methods e.g. see: Hao & Prosperetti JCP 2004, or sharp interface cartesian method by S. H. Udaykumar in JCP

a commnet: you can use variable density formulation, e.g.

rho = vol_frac * rho_flo + (1-vol_frac) * rho_virtual

ratio = rho_flow/rho_virtual

ratio >> 1

  Reply With Quote

Old   February 27, 2010, 06:35
Default
  #3
Senior Member
 
Claus Meister
Join Date: Aug 2009
Location: Wiesbaden, Germany
Posts: 241
Rep Power: 9
idrama is on a distinguished road
Hello vadim,

you said "velocities can fluctuate widely". Could it be that during the simulation the time steps becomes smaller and smaller. My question based on the a problem i have. My simulation runs between 0s and 0.6 s, and in time of 0.18s simulation time the time steps, which are dependent on CFL number (bounded by 0.5), getting smaller and smaller and evetnually the simulation abords.

cheers,
idrama is offline   Reply With Quote

Old   February 27, 2010, 06:36
Default
  #4
Senior Member
 
Claus Meister
Join Date: Aug 2009
Location: Wiesbaden, Germany
Posts: 241
Rep Power: 9
idrama is on a distinguished road
Furthermore, should our problems be related then I want changes my question: how can i avoid it?
idrama is offline   Reply With Quote

Old   February 28, 2010, 18:54
Default reference
  #5
Senior Member
 
CFDtoy
Join Date: Mar 2009
Location: United States
Posts: 145
Blog Entries: 2
Rep Power: 9
CFDtoy is on a distinguished road
Hi there,
Could you kindly post your reference where they indicate as alpha -> 0, vel -> high values?

Thanks,

CFDtoy

Quote:
Originally Posted by Zak
;58123
In the Eulerian two-fluid model for two-phase flows, the standard formulation for the momentum equations becomes singular as the volume fractions tend to zero. Some papers suggest that resulting velocities can fluctuate widely in the regions where volume fractions tend to vanish.

How do you deal with the problem of singularity in your code?

Or could you give me some effective suggestions for the problem or references about Eulerian-Eulerian Model?

Thanks!
__________________
CFDtoy
CFDtoy is offline   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
Concentric tube heat exchanger (Air-Water) Young CFX 5 October 6, 2008 23:17
Mixture and Eulerian Model Hassid S. FLUENT 1 August 9, 2007 07:24
Eulerian Model Hassan FLUENT 2 September 7, 2006 07:17
the interface bc in Eulerian Model lily FLUENT 0 July 28, 2005 02:37
Two phase Eulerian Model Problem senthil FLUENT 5 May 21, 2003 02:55


All times are GMT -4. The time now is 02:57.