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

planning hull

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   February 18, 2010, 12:58
Default planning hull
  #1
Member
 
Ciro Cannavacciuolo
Join Date: Mar 2009
Posts: 35
Rep Power: 17
mach000 is on a distinguished road
Hi to everybody,
i'm an aerospace engineer and I'm working as CFD and Structural Engineer.
For my simulation I use Ansys CFX v11.
Most of my simulations are about multiphase flowfields. I've simulated semi submerged rudder, flaps and also a semi submerged propeller (there are two videos about it on youtube. Look for "cfd semi submerged propeller").
Now, I'm trying to simulate planing hulls but i've a great problem.
A very thin air layer appears between the hull and the free surface. Infact, at the and of the simulation the hull is completely dry.
i would like to know if someone studied this kind of simulation and have some idea or solution of this problem.
Thank you very much to everyone!

Last edited by mach000; February 25, 2010 at 05:42.
mach000 is offline   Reply With Quote

Old   February 18, 2010, 18:02
Default
  #2
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,665
Rep Power: 143
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
I think you will need to go to the literature for this. I doubt you will find people with experience in a specialised area like this on the forum (but you never know your luck).
ghorrocks is offline   Reply With Quote

Old   February 24, 2010, 03:42
Default
  #3
Senior Member
 
stephane sanchi
Join Date: Mar 2009
Posts: 314
Rep Power: 18
openfoam_user is on a distinguished road
Hi Ciro,

could you give me our personal email address at Victory Design.

I will write you soon.

Stephane.
openfoam_user is offline   Reply With Quote

Old   February 24, 2010, 04:38
Default
  #4
Member
 
Ciro Cannavacciuolo
Join Date: Mar 2009
Posts: 35
Rep Power: 17
mach000 is on a distinguished road
Quote:
Originally Posted by openfoam_user View Post
Hi Ciro,

could you give me our personal email address at Victory Design.

I will write you soon.

Stephane.

Hi stephane,
you can write me at victory@victory.it

Thank you

Ciro
mach000 is offline   Reply With Quote

Old   February 24, 2010, 05:34
Default
  #5
Member
 
Ciro Cannavacciuolo
Join Date: Mar 2009
Posts: 35
Rep Power: 17
mach000 is on a distinguished road
Dear Stepane,
if you want you can write me at my personal mail address cannavacciuolociro@gmail.com.

Bye

Ciro
mach000 is offline   Reply With Quote

Old   February 24, 2010, 12:22
Default
  #6
Member
 
Ciro Cannavacciuolo
Join Date: Mar 2009
Posts: 35
Rep Power: 17
mach000 is on a distinguished road
Hi Stephane,
i received your email at victory address.
First of all, thank you very much for the instructions that yuo gave me.
I'll start some simulation in order to set all the parameters.
You told me about a newsletter that you sent me today, but i never received it.
I don't know openfoam but now I'll try to have some news about it.
If you can, and you you want, i would like to continue to have contact with you in order to share ideas and "problems". In order to have the possibility to read your message in every moment, I prefer to receive your msg in this forum or at my private address (cannavacciuolociro@gmail.com). I hope it will not be a problem for you. Thank you very much.
Ciro
mach000 is offline   Reply With Quote

Old   May 11, 2011, 03:37
Default
  #7
New Member
 
ZS
Join Date: Mar 2009
Posts: 24
Rep Power: 17
ziyasaydam is on a distinguished road
Dear all,

I am experiencing a very similar problem with Star-CCM and Fluent during analysis of a planing yacht. As speeds are increased (and hence the trim) a layer of air travels aft below the hull and the bottom of the hull dries...

Could you please share how you managed to overcome the situation?

Kind regards,

Ziya
ziyasaydam is offline   Reply With Quote

Old   May 11, 2011, 07:49
Default
  #8
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,665
Rep Power: 143
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
I would imagine in this case the air under the hull would form a very thin layer. You will need a fine mesh to resolve this thin air layer. Have you done a mesh refinement check to ensure it is not fixed by simply a finer mesh?
ghorrocks is offline   Reply With Quote

Old   May 11, 2011, 07:55
Default
  #9
New Member
 
ZS
Join Date: Mar 2009
Posts: 24
Rep Power: 17
ziyasaydam is on a distinguished road
Actually, the problem gets worse as the mesh gets finer.
If the mesh is coarsened and the boundary layer mesh is not applied, the air film under the hull no longer forms. But then, the wall treatment is no longer valid and the drag values are no longer reliable...
ziyasaydam is offline   Reply With Quote

Old   May 11, 2011, 08:29
Default
  #10
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,665
Rep Power: 143
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
Quote:
Actually, the problem gets worse as the mesh gets finer.
Then is sounds like you are a long way away from an adequate mesh. You need to go much finer until it starts to converge.

Of course a coarser mesh makes it disappear - the thin layer is smeared across a big element and quickly dissipates. The wall treatment and drag is the least of your worries. You need a mesh fine enough to resolve the feature.
ghorrocks is offline   Reply With Quote

Old   August 9, 2013, 17:17
Default air phase being formed on the bottom of the hull
  #11
New Member
 
Deepak Bansal
Join Date: Jul 2013
Posts: 9
Rep Power: 12
Deepak Bansal is on a distinguished road
hey buddy i am also facing same problem in planing craft that air phase being formed on the bottom of the hull.................how did u solve this problem.................reply as soon as possible...............
Deepak Bansal is offline   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
planning hulls Ciro Cannavacciuolo CFX 7 August 9, 2013 17:12
Lift on the Hull hashem_1064 CFX 10 May 28, 2009 19:23
Mesh Motion pitch on a hull Seb CFX 1 February 23, 2009 14:04
software for planning hull Ciro Cannavacciuolo Main CFD Forum 7 December 12, 2008 04:26
Pressure distribution along hull sam CFX 1 September 13, 2008 18:09


All times are GMT -4. The time now is 10:37.