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

Size functions and boundary layer with Gambit 2.2

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

Reply
 
LinkBack Thread Tools Display Modes
Old   July 21, 2006, 04:45
Default Size functions and boundary layer with Gambit 2.2
  #1
Ramine
Guest
 
Posts: n/a
Hi all!

I'm fairly new to CFD and I'm trying to model 3D wings in order to compare their induced drag in function of their shape (racked wing tip, twisted wing, tapered, winglets...)

After spending some time reading the forum, I came to the conclusion that using the Boundary layer tool in Gambit will not work in 3D for a newbie like me and that size function could do the trick.

I'm not sure I need a fine boundary layer for my study as the wing is meant to be a hydrofoil working at low Re (working Re between 300k and 600k).

Anyway, I'm wondering how you guys would mesh these wings. Would you only use size functions? Looks like if I want to have my first few cells in the 30-300y+ region I'm gonna need a lot of cells arround my wing.

I have a fairly limited CPU ressource so max number of cells I'm expecting is arround 800k - 1M.

I'm also thinking of only using the laminar solver in Fluent as the Re is low and I don't think I really need a turbulence model for this comparison study. Would this assumption sound right?

any thoughts or tips I could use for my study?

Thanks in advance,

Ramine
  Reply With Quote

Old   July 21, 2006, 21:27
Default Re: Size functions and boundary layer with Gambit
  #2
Nanda
Guest
 
Posts: n/a
i think the Reynolds number that you mentioned 300K to 600K should require turbulence model.nonetheless, the laminar solver that you mentioned can be used at first and later on the turbulence model can be switched on. to model the wing, why not just try the boundary layer tool first and examine the results?

  Reply With Quote

Old   July 22, 2006, 05:13
Default Re: Size functions and boundary layer with Gambit
  #3
Ramine
Guest
 
Posts: n/a
Hi,

Thanks for your reply. I've tried the boundary layer tool already but without success. Also, I want to have a mesh as similar as possible between all the wings I'll be testing.

Could I mesh on Gambit without the boundary layer tool and refine the mesh arround the foil in fluent afterwards?

Cheers,

Ramine
  Reply With Quote

Old   July 23, 2006, 19:34
Default Re: Size functions and boundary layer with Gambit
  #4
Ramine
Guest
 
Posts: n/a
ok,

I've managed to mesh my first wing using a curvature size function for the wing faces, a mesh size function for the symetry plane and a fixed size function for the volume mesh with the wing mesh as source. I get a reasonable mesh with about 900k cells before refining it in Fluent.

But I've been trying to do exactly the same thing on my second wing (I've added a raked tip on it) and I can't get Gambit to mesh it... I've checked if the tree size was enough, the worst skewed cell I have is about 0.47 and still, Gambit fails by saying that the problem comes usually from my faces skewness bla bla bla...

I'm not clever enough to understand all the meanings of the default settings in the Gambit help so does anybody knows what should I change?

Maybe the fact that I have a virtual volume doesn't help? But I can't change it to real anyway...

regards,

Ramine
  Reply With Quote

Old   August 1, 2006, 08:54
Default Re: Size functions and boundary layer with Gambit
  #5
Riaan
Guest
 
Posts: n/a
If you are willing to go to a hybrid mesh, I would recommend you use TGRID to generate the boundary layers. Build the surface meshes in Gambit and then add 5-10 prismatic boundary layer cells on top of that.

I have been studying winglets as well and would be interested in seeing some of your results. Please send me an email and we can talk.
  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
Wind turbine simulation Saturn CFX 34 October 16, 2014 05:27
RPM in Wind Turbine Pankaj CFX 9 November 23, 2009 05:05
gambit size functions from boundary layer cap Greg FLUENT 1 March 11, 2006 12:04
New topic on same subject - Flow around race car Tudor Miron CFX 15 April 2, 2004 06:18
Please help with flow around car modelling! Tudor Miron CFX 17 March 19, 2004 20:23


All times are GMT -4. The time now is 15:17.