CFD Online URL
[Sponsors]
Home > Forums > CFX

turbulence modeling error at a stagnation point

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

Reply
 
LinkBack Thread Tools Display Modes
Old   August 8, 2006, 05:26
Default turbulence modeling error at a stagnation point
  #1
erdem
Guest
 
Posts: n/a
hi

I'm studying external aerodynamics of Ahmed Body car geometry. I have used realizable k-eps, SST k-omega and RSM models. in terms of drag coefficient I got similar values with all models. but all of them calculated nearly 1.5-2 times drag at the front of the body (comparing with the original experiments. Realizable k-epsilon has the highest drag on the front.

why does this happen? would you please help me about investigating the greater pressures at the front caused by turbulence modeling? I have to write a discussion about it. this is really important. thanks for you time.

Erdem
  Reply With Quote

Old   August 8, 2006, 23:48
Default Re: turbulence modeling error at a stagnation poin
  #2
Glenn Horrocks
Guest
 
Posts: n/a
Hi,

What do you mean by drag at the front of the body?

There is a validation case of the Ahmed body in the CFX-Community pages. I think you will find you will need LES/DES or SAS to get good drag results on the Ahmed body. It is a very challenging thing to get accurate results on.

Glenn Horrocks
  Reply With Quote

Old   August 9, 2006, 03:04
Default Re: turbulence modeling error at a stagnation poin
  #3
IMAD
Guest
 
Posts: n/a
I THINK YOU NEED TO REFIN MESH NEAR THE STAGNATION POINT WHERE VERY HIGH GRADIENT EXSIT
  Reply With Quote

Old   August 9, 2006, 20:54
Default Re: turbulence modeling error at a stagnation poin
  #4
Glenn Horrocks
Guest
 
Posts: n/a
Hi Imad,

It has been shown by many studies that a steady state assumption with RANS turbulence models of bluff body flows often leads to poor drag accuracy. There is only so far the extra grid refinement will go to improving accuracy if the fundamental physics are not being modelled correctly.

Glenn Horrocks
  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
block-structured mesh for t-junction Robert@cfd ANSYS Meshing & Geometry 20 November 11, 2011 05:59
Turbulence postprocessing Mohsin FLUENT 0 September 19, 2011 22:05
CFD-Wiki Monthly Focus Area: Turbulence Modeling Jonas Larsson Main CFD Forum 0 May 6, 2006 20:08
Turbulence Modeling RAJURAMAIAH Main CFD Forum 10 August 29, 2004 16:17


All times are GMT -4. The time now is 14:04.