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

Grid adaption

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   December 31, 2009, 06:19
Default Grid adaption
  #1
New Member
 
Join Date: Dec 2009
Location: Italy
Posts: 23
Rep Power: 16
SerSe is on a distinguished road
Hi guys,

I have a capillary pipe with two fluid phases, i.e., water at the left and right end of the pipe separated by an air gap (therefore a unique big bubble which bounds the walls) in the centre of the pipe.
My BC are mass flow inlet (just water) and pressure outlet, interior at the interfaces water/air/water and, of course, walls.
I am using the Volume of Fluid Multi-phase model to get insight into both the motion of the air gap pushed by the inlet water and the shape of the interface.
Should I turn grid adaption on, to model this problem?
and should I also provide as input in Fluent the motion of the interiors?

I made some trials with dynamic mesh but it didn't work. Moreover, dynamic mesh is used when the motion of a certain domain is known, while I don't know the motion law of the bubble.

Many thanks,

SerSe
SerSe is offline   Reply With Quote

Old   January 14, 2010, 10:45
Default
  #2
meb
Member
 
Marco Evangelos Biancolini
Join Date: May 2009
Location: Rome - Italy
Posts: 80
Rep Power: 16
meb is on a distinguished road
Quote:
Originally Posted by SerSe View Post
Hi guys,

I have a capillary pipe with two fluid phases, i.e., water at the left and right end of the pipe separated by an air gap (therefore a unique big bubble which bounds the walls) in the centre of the pipe.
My BC are mass flow inlet (just water) and pressure outlet, interior at the interfaces water/air/water and, of course, walls.
I am using the Volume of Fluid Multi-phase model to get insight into both the motion of the air gap pushed by the inlet water and the shape of the interface.
Should I turn grid adaption on, to model this problem?
and should I also provide as input in Fluent the motion of the interiors?

I made some trials with dynamic mesh but it didn't work. Moreover, dynamic mesh is used when the motion of a certain domain is known, while I don't know the motion law of the bubble.

Many thanks,

SerSe
With VOF the boundary movements is not a concern; the ability to carefully track the sepration between phases depends on the mesh size.
You have to turn on dynamic mesh if external boundaries moves.
We are study a similar application (but on a different scale): a flexible pipe partially filled with liquid... In our application you need both VOF and moving mesh.
meb is offline   Reply With Quote

Old   February 3, 2010, 05:40
Default
  #3
New Member
 
Join Date: Dec 2009
Location: Italy
Posts: 23
Rep Power: 16
SerSe is on a distinguished road
Hi Meb,
after some trials I got that I just need to use the VOF model, without using any dynamic mesh, since my boundaries are fixd walls.

By the way, when you talk about refining the mesh to catch the right interface shape, do you refer to the mesh size in the radial direction or in the axial direction? I guess the axial mesh would affect that shape more than the radial one.

Greetings,

Serse
SerSe is offline   Reply With Quote

Old   February 3, 2010, 06:35
Default
  #4
meb
Member
 
Marco Evangelos Biancolini
Join Date: May 2009
Location: Rome - Italy
Posts: 80
Rep Power: 16
meb is on a distinguished road
Quote:
Originally Posted by SerSe View Post
Hi Meb,
after some trials I got that I just need to use the VOF model, without using any dynamic mesh, since my boundaries are fixd walls.

By the way, when you talk about refining the mesh to catch the right interface shape, do you refer to the mesh size in the radial direction or in the axial direction? I guess the axial mesh would affect that shape more than the radial one.

Greetings,

Serse
Using VOF you track the interface as a concentration. The ability to resolve the interface using VOF is strongly related to local mesh size.
So the CFD domain part where the interface is moving has to be equally spaced using a fine mesh size (in both directions).

We have used such technique here:

L. Andreassi, R. Baudille, M. E. Biancolini, “ Spew Formation in a single lap joint” International Journal of Adhesion & Adhesives 27 (2007) 458–468.

R. Baudille, M. E. Biancolini, “A general approach for studying the motion of a cantilever beam interacting with a 2D fluid flow” Interaction and Multiscale Mechanics, Vol. 1, No. 4 (2008) 000-000 1

Regards.

Marco
meb is offline   Reply With Quote

Old   February 3, 2010, 07:58
Default
  #5
New Member
 
Join Date: Dec 2009
Location: Italy
Posts: 23
Rep Power: 16
SerSe is on a distinguished road
Hi Marco,

a quick question.. is there any possibility in Fluent to model only half a curved pipe section (let's say a pipe with a 90° curve) and solve it as 2D axisymmetric?

Thanks for the tips on mesh size when using the VOF model!

Ciao,

Serse
SerSe is offline   Reply With Quote

Old   February 3, 2010, 08:21
Default
  #6
meb
Member
 
Marco Evangelos Biancolini
Join Date: May 2009
Location: Rome - Italy
Posts: 80
Rep Power: 16
meb is on a distinguished road
I don't know, but the mentioned problem is not axis-symmetric!
meb is offline   Reply With Quote

Reply

Tags
dynamic mesh, grid adaption, moving mesh, vof model

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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 Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
grid adaption mode NOT selectable via VNC Ralf Schmidt FLUENT 2 May 24, 2006 03:35
Need help with Grid Adaption _stephen_ FLUENT 0 January 13, 2005 08:07
Adaption by Y+ on a mixed grid with periodics Martin Shanel FLUENT 0 June 24, 2002 07:31
Combustion Convergence problems Art Stretton Phoenics 5 April 2, 2002 06:59
Grid Adaption problems Jie FLUENT 1 February 26, 2002 12:03


All times are GMT -4. The time now is 12:28.