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

Which model should I choose?

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

Reply
 
LinkBack Thread Tools Display Modes
Old   June 5, 2013, 19:50
Smile Which model should I choose?
  #1
Senior Member
 
Dongyue Li
Join Date: Jun 2012
Location: Torino, Italy
Posts: 676
Rep Power: 8
sharonyue is on a distinguished road
Hi All,

Recently I am uncertain which model I should use in my project. Its a gas-liquid mixing system, but the liquid is xanthan gum. When gas is injected into xanthan gum. the flow type is kind like slug flow. Look the image 3, So there are many fine bubbles and some big gas slugs. Until now I am willing to choose VOF or Euler-Euler model.

1. Regarding VOF, as of the mesh reason, in the simulation there would not have this fine bubbles. but I can have this big gas slugs.

2. Reagrding Euler-Euler model, I am not sure what the reault looks like. I only made a test about air-water system. But I heard two fluid model cannot deal with seperation rite?

Any ideas ?


BTY, in experiment, which method do you use if you want to get global gas hold up or local bubble size? Now I am using expansion technique. But the liquid level fluctuate woo much which affect my global gas hold up badly.

Thanks in advance.
Attached Images
File Type: jpg 1.jpg (61.2 KB, 23 views)
sharonyue is offline   Reply With Quote

Old   June 6, 2013, 05:40
Default
  #2
Senior Member
 
OJ
Join Date: Apr 2012
Location: United Kindom
Posts: 475
Rep Power: 11
oj.bulmer will become famous soon enough
VOF seems a strong contender. Since the the bubbles are of really large size having a distinct interface. But be aware that you will need a very fine mesh if you want to capture the interface.

Quote:
Reagrding Euler-Euler model, I am not sure what the reault looks like. I only made a test about air-water system. But I heard two fluid model cannot deal with seperation rite?
Euler model is great for dispersed bubbles and the additional population models can also model the coalescence and breakup. But I don't think you are look for this.

I was wondering, if this is a tank, do you specify the top surface as free surface or degassing boundary condition (using UDF)?

OJ
oj.bulmer is offline   Reply With Quote

Old   June 6, 2013, 23:36
Default
  #3
Senior Member
 
Dongyue Li
Join Date: Jun 2012
Location: Torino, Italy
Posts: 676
Rep Power: 8
sharonyue is on a distinguished road
Quote:
Originally Posted by oj.bulmer View Post
VOF seems a strong contender. Since the the bubbles are of really large size having a distinct interface. But be aware that you will need a very fine mesh if you want to capture the interface.



Euler model is great for dispersed bubbles and the additional population models can also model the coalescence and breakup. But I don't think you are look for this.

I was wondering, if this is a tank, do you specify the top surface as free surface or degassing boundary condition (using UDF)?

OJ
Hi OJ,

I am using OpenFOAM, I dont need to specify the gas-liquid interface's B.C. in the tank's outlet, I make U's zerogradient and pressure is fixedvalue. so in FLUENT I am not quite familiar with that, Sorry about that.

In OpenFOAM, there is no PBM, so I have to implent it by myself which its very tough for me.

Regarding VOF, Have you ever made a test to see the viscosity field? I have some of this unnormal viscosity problems...In OpenFOAM, if the liquid's viscosity is changing (non-newtonian fluid), all of the viscosity include the air's is the same. I dont know if this exists in FLUENT?

Thanks for your reply.
sharonyue is offline   Reply With Quote

Old   June 7, 2013, 06:52
Default
  #4
Senior Member
 
OJ
Join Date: Apr 2012
Location: United Kindom
Posts: 475
Rep Power: 11
oj.bulmer will become famous soon enough
I see, I think you are on the wrong forum then. Try posting it on OPENFoam forum?

OJ
oj.bulmer 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
What turbulent flow model choose in Fluent ja.maldonado1187 FLUENT 2 August 11, 2013 06:33
2 stage axial turbine model convergence issues sherifkadry CFX 2 September 7, 2009 20:51
multi fluid mixture model issue rystokes CFX 3 August 9, 2009 19:13
what constants to choose for std k-e model daniel.struwig FLUENT 0 April 18, 2009 06:51
Advanced Turbulence Modeling in Fluent, Realizable k-epsilon Model Jonas Larsson FLUENT 5 March 13, 2000 04:27


All times are GMT -4. The time now is 08:53.