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

Turbulence Model and Meshing Advice

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

Reply
 
LinkBack Thread Tools Display Modes
Old   January 31, 2006, 10:18
Default Turbulence Model and Meshing Advice
  #1
Jason
Guest
 
Posts: n/a
I have a complex bluff body with cavities, gaps, and fins protruding from the body. I was asked to get the unsteady frequencies coming off these different features at compressible subsonic speeds (about Mach .5, and ignoring Fluid-Structure-Interaction, which we simply can't handle here).

I'm assuming this will get too complex for a realizable k-ep model, but can an RSM handle this, or do I have to go with an LES model? Also, as far as meshing goes, can I get away with using y+ values of around 30, or do I have to bring the mesh down to y+ value of around 1?

Any other advice is greatly appreciated as well.

Thanks, Jason
  Reply With Quote

Old   January 31, 2006, 14:05
Default Re: Turbulence Model and Meshing Advice
  #2
Razvan
Guest
 
Posts: n/a
I say that RSM will do the job respectably, even with y+=30, of course taking care to have a REAL B-L mesh (6-7 or better 10 layers, with lowest skewness possible), at least 2nd order discretisation and well resolved wakes. The only thing I'm worried about is the actual frequencies values you will obtain with RSM...

LES (or better DES in your case) will certainly do a much better job. One thing: computational effort with DES might be almost equal to a ordinary k-e unsteady calculation(I say this because I oftenly encountered this situation when doing my own calculations)!

Beware: DES comp. effort = k-e unsteady comp. effort means same CPU time for a time step! But that's it! The "problem" with DES is that you'll absolutely need more and sometimes smaller time steps to really converge the solution.

Anyway, if precision is what you're looking for, take DES. My advice.

Good luck, Razvan
  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
[ANSYS Meshing] ANSYS Meshing hangs at "Preparing to model boundary for part" jonny_b ANSYS Meshing & Geometry 12 June 12, 2012 01:55
[ANSYS Meshing] Advice for meshing of corrugated tubes subsemitonium ANSYS Meshing & Geometry 15 July 1, 2011 16:12
2D Meshing - No matter how thin my model is, it is still 2 elements thick RossFS ANSYS Meshing & Geometry 6 April 14, 2010 00:13
[GAMBIT] Desperate student needs help meshing 3D GAMBIT model - please help! lau06165 ANSYS Meshing & Geometry 1 March 22, 2010 02:09
Meshing Techniques & k-omega turbulence model Nurul Murad FLUENT 1 April 2, 2004 12:19


All times are GMT -4. The time now is 19:22.