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

A big ball moves in liuid?

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   September 4, 1998, 09:07
Default A big ball moves in liuid?
  #1
sheng
Guest
 
Posts: n/a
Dear Gentleman,

The process is liquid emptying out from the container, then a ball (big, not a particle) will move with the liquid to the outlet.

I want to model this process. It seems the first big-stone in front of me is that the grid problem. How can I design the moving grid of the ball?

I'd like to hear your good feeling on modeling this process

Thx a lot

sheng
  Reply With Quote

Old   September 4, 1998, 16:52
Default Re: A big ball moves in liuid?
  #2
C-H Kuo
Guest
 
Posts: n/a
If you are choosing commercial code to do the work, a friend from Ricardo told me their code is good in moving mesh. based on predicted moving object positions, you set up several stages of mesh before computation. After compress/stretch mesh to a certain degree, map the solution of current stage onto new mesh of next stage in computation. The stretch and squeeze of mesh will be kept to minimal. You can contact www.ricardo.com for details.

If ball motion is unknown, you are coding the solver, and you don't want to remap solution or over stretch the mesh, I would try to use porosity in stationary mesh. The liquid fraction is 0 when an element is fully occupied by the ball, and 0~1 when partiall occupied. This approach is easier to program, but the accuracy for boundary layer around the ball is a problem.

  Reply With Quote

Old   September 5, 1998, 22:33
Default Re: A big ball moves in liuid?
  #3
Adrin Gharakhani
Guest
 
Posts: n/a
You haven't specified the problem exactly, so the operating parameters are unknown (e.g., volumetric flow rate, relative size of the ball to the container and the exit port, the extent to which you wish to get a solution - do you want to see a solution up to the point that the ball reaches the exit port or including its motion through the port, etc.)

The reason for the above questions is simple: Sometimes we tend to over-complicate analytically simple problems by solving them using CFD.

Depending on the complexity of the problem, you can get quite accurate solutions using basic 1-D type flow analysis and your fluids knowledge. Try this route first before you spend alot of time worrying about meshing.

Adrin Gharakhani, Sc.D.
  Reply With Quote

Old   September 6, 1998, 11:27
Default Re: A big ball moves in liuid?
  #4
sheng
Guest
 
Posts: n/a
This is emptying process. Due to gravity force, the liquid in the container will flow through the bottom outlet. When the bath height decrease, the concentration of inclusion will increase at outlet.

Then, we want to put a big ball as a flow control device in order to prevent some inclusion particles flow out.

If without ball, I can simulate the process as a typical filling-out process (the container is 3D clinder). The predicted inclusion concentration at outlet also can be predicted. Now, considering A BIG BALL, I can put a 2D circle inside a 2D plane (by embedding-fine grid or multi-block), however, I am really confuse on how to put a 3D sphere into a clinder. By the way, I use commerical software based on FDM as grid generation tool.

Thanks a lot for your kind suggestion!

Sheng

  Reply With Quote

Reply

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
modeling freestream in an big Volume with gravity Raambi STAR-CCM+ 1 May 10, 2011 08:04
Floating ball on free surface validations Bak_Flow FLUENT 0 November 10, 2008 17:30
Floating ball on free surface validations Bak_Flow Main CFD Forum 0 November 10, 2008 16:57
BIg BIg Problems....SUPERSONIC FLOW OVER A FLAT PL edison Main CFD Forum 7 October 11, 2005 10:34
rotating ball Jen FLUENT 1 June 14, 2005 15:16


All times are GMT -4. The time now is 18:03.