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

simulation of free falling sphere into calm water?

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

Reply
 
LinkBack Thread Tools Display Modes
Old   September 1, 2010, 00:05
Default simulation of free falling sphere into calm water?
  #1
New Member
 
pedram
Join Date: Aug 2010
Posts: 8
Rep Power: 6
pedyspider is on a distinguished road
hi there,
i'm somehow new to cfx and want to model a free falling sphere into calm water.
can anyone help me how to start?
previously i've done a 2D simulation of flow around airfoil, using FLUENT.
pedyspider is offline   Reply With Quote

Old   September 1, 2010, 20:02
Default
  #2
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,796
Rep Power: 84
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
A sphere of what? A fluid or is it rigid? What do you want to get out of the simulation?
ghorrocks is online now   Reply With Quote

Old   September 2, 2010, 00:56
Default
  #3
New Member
 
Join Date: May 2009
Posts: 8
Rep Power: 8
Nevel is on a distinguished road
If the sphere is rigid you can easely use Immersed Body Method (new CFX v12 feature).
Nevel is offline   Reply With Quote

Old   September 2, 2010, 05:51
Default
  #4
New Member
 
mikey
Join Date: Aug 2010
Posts: 5
Rep Power: 6
bionic is on a distinguished road
Hi pedram
I have a paper that's exactly what you want.
Also u can speak to me more easier
I'm saeed
bionic is offline   Reply With Quote

Old   September 3, 2010, 13:36
Default
  #5
New Member
 
pedram
Join Date: Aug 2010
Posts: 8
Rep Power: 6
pedyspider is on a distinguished road
it's a rigid sphere, with density less than water, i want to calculate the time it take for maximum penetrate, and the penetration depth.
pedyspider is offline   Reply With Quote

Old   September 4, 2010, 06:41
Default
  #6
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,796
Rep Power: 84
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
The immersed solid feature would be the easiest way to get this going. 6DOF is a beta option for V12 but fully supported in V13 - talk to your CFX support person to get the preview version (it is on the ANSYS Customer web page).
ghorrocks is online now   Reply With Quote

Old   September 5, 2010, 07:09
Default
  #7
New Member
 
pedram
Join Date: Aug 2010
Posts: 8
Rep Power: 6
pedyspider is on a distinguished road
i've read a tutorial here wich told this about immersed solid
"transient runs should be incompressible and single phase."

but my question was a solid sphere that will fall from air into a calm water which is a multiphase problem.
can i use re-meshing or moving mesh?
pedyspider is offline   Reply With Quote

Old   September 5, 2010, 20:16
Default
  #8
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,796
Rep Power: 84
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
There are examples of floating objects with a free surface model available from CFX support. Talk to CFX support to get them.

I was not aware of the single phase limitation - are you sure this is correct? Has CFX V13 overcome this limitation?
ghorrocks is online now   Reply With Quote

Old   May 25, 2012, 06:17
Default
  #9
New Member
 
belgacem
Join Date: Jan 2012
Posts: 22
Rep Power: 5
belgacem is on a distinguished road
Hi Friends
I am also studying immersed boundary method and and try to simulate a block falling in the water. I am using "immersed solid" then rigid body 6DOF and I let it fall freely but it can't stoped in the bottom where the velocity must be zero. I give a density to the block and i let it fall freely under gravity. Noted that the rigid body is defined as an immersed solid. i have specified a stationary coordinate frame that has its origin at the center of mass of the physical rigid body. Another fixed coordinate frame was specified related to the water at rest.
What can I do to stopped the rigid body in the bottom where the potentiel energy must be zero?

thank you!
belgacem is offline   Reply With Quote

Old   May 25, 2012, 15:34
Default
  #10
New Member
 
pedram
Join Date: Aug 2010
Posts: 8
Rep Power: 6
pedyspider is on a distinguished road
as the 2.5D simulation i've done, i hadn't used immersed body, as i told it's for single phase fluid. they may improved it in cfx 13, which i'm not aware.

i've used motion specified option for the solid wedge boundries, and applied free falling equation motion to it:
d2=ft^2/m-gt^2+vt+d1

i hope this help!
pedyspider is offline   Reply With Quote

Old   December 24, 2012, 03:40
Default
  #11
New Member
 
Vinu
Join Date: Jun 2012
Posts: 3
Rep Power: 5
vinu2907 is on a distinguished road
Quote:
Originally Posted by bionic View Post
Hi pedram
I have a paper that's exactly what you want.
Also u can speak to me more easier
I'm saeed
Hai bionic/ saeed,

Can you please post the paper that you are talking about?
vinu2907 is offline   Reply With Quote

Old   December 24, 2012, 03:45
Default
  #12
New Member
 
Vinu
Join Date: Jun 2012
Posts: 3
Rep Power: 5
vinu2907 is on a distinguished road
Quote:
Originally Posted by pedyspider View Post
as the 2.5D simulation i've done, i hadn't used immersed body, as i told it's for single phase fluid. they may improved it in cfx 13, which i'm not aware.

i've used motion specified option for the solid wedge boundries, and applied free falling equation motion to it:
d2=ft^2/m-gt^2+vt+d1

i hope this help!
Hai pedram,

Have you solved the problem of the sphere falling into calm water?. I'm also trying to simulate similar problem. Its also a sphere falling into water. I'm also trying to get the maximum penetration depth etc. If you have solved, can you please help me in this regard. I'm new to CFX command language.
vinu2907 is offline   Reply With Quote

Old   January 1, 2013, 13:44
Default
  #13
New Member
 
pedram
Join Date: Aug 2010
Posts: 8
Rep Power: 6
pedyspider is on a distinguished road
yes, i've solved it with CFX
look for "motion specified" option for sphere wall boundaries, and specify the displacement or position by CEL
this may help:
https://www.sharcnet.ca/Software/Flu.../i1304009.html

pedyspider is offline   Reply With Quote

Old   September 3, 2013, 09:49
Default
  #14
New Member
 
Mondi
Join Date: Sep 2013
Posts: 2
Rep Power: 0
Mondi is on a distinguished road
Hi Pedram
Would you modify your suggested link I can not open it?
and any body know about floating object or immersed solids tutorial (buoy) tutorial? where i can find it?

Mondi is offline   Reply With Quote

Old   September 25, 2013, 03:22
Cool
  #15
Member
 
Centurion2011's Avatar
 
Join Date: Jul 2011
Posts: 72
Blog Entries: 1
Rep Power: 10
Centurion2011 will become famous soon enough
Did you try tutorial "Falling box" first? Using 6DOF solver and remeshing is your best bet

you can download tutorial here
__________________
I'M NOT A GYNECOLOGIST BUT I'LL TAKE A LOOK.
Centurion2011 is offline   Reply With Quote

Old   September 25, 2013, 10:16
Default
  #16
New Member
 
Mondi
Join Date: Sep 2013
Posts: 2
Rep Power: 0
Mondi is on a distinguished road
Quote:
Originally Posted by Centurion2011 View Post
Did you try tutorial "Falling box" first? Using 6DOF solver and remeshing is your best bet

you can download tutorial here

dear sir
i can not download it would you send it to my mail?
Saiiid1001@yahoo.com
Mondi is offline   Reply With Quote

Old   September 25, 2013, 14:32
Default
  #17
Member
 
Centurion2011's Avatar
 
Join Date: Jul 2011
Posts: 72
Blog Entries: 1
Rep Power: 10
Centurion2011 will become famous soon enough
OK I'll send it to you tomorrow
__________________
I'M NOT A GYNECOLOGIST BUT I'LL TAKE A LOOK.
Centurion2011 is offline   Reply With Quote

Old   June 25, 2015, 11:03
Default
  #18
New Member
 
Aman Jain
Join Date: Jun 2015
Posts: 1
Rep Power: 0
amanjain058 is on a distinguished road
I am trying the free falling box 2D . I am following the exact steps in tutorial . Except I am interpreting the UDF ,which I think is fine ? . I am getting negative mesh . Does the result depend on the size of time step ?. When I give other time steps the box goes out of the boundaries . Please can you help me ?
Thanks .
amanjain058 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
water jet simulation Gajanan Kale FLUENT 3 July 14, 2009 16:21
Air and water simulation Mavinakere CD-adapco 1 February 27, 2002 23:35
uptodate water distribution network fredius,magige,tanzanian,(e.a) Main CFD Forum 0 January 27, 2002 08:10
Asymmetric water free jet study Norberto Parreira Main CFD Forum 7 June 25, 2001 08:23
sphere in a free surface (thin film)flow Vasu Veerapaneni Main CFD Forum 0 September 15, 1998 17:32


All times are GMT -4. The time now is 05:46.