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

Ansys 12, Fluent, SST Transition models

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

Like Tree1Likes
  • 1 Post By bugra

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   July 12, 2010, 04:31
Default Ansys 12, Fluent, SST Transition models
  #1
Member
 
B. Selenbas
Join Date: Dec 2009
Posts: 37
Rep Power: 16
bugra is on a distinguished road
Hi,

I'm working on a laminer-turbulence seperation problem and want to use the new transition models in Fluent (ansys 12) version. I could not find any guide that presents the related equations. Has anybody got any information about these new turbulence models?

Thanks
kinger likes this.
bugra is offline   Reply With Quote

Old   July 12, 2010, 11:17
Default
  #2
Senior Member
 
Join Date: Apr 2009
Posts: 531
Rep Power: 20
stumpy is on a distinguished road
Take a look in the CFX documentation (you'll have to install CFX). The formulation is there and should be the same as Fluent.
stumpy is offline   Reply With Quote

Old   July 13, 2010, 07:25
Default
  #3
New Member
 
NeNaD
Join Date: Mar 2010
Posts: 16
Rep Power: 16
skinnyfluid is on a distinguished road
Bugra,

I think that this may helps you:

Boundary Conditions/Inlet/Intermittency (this is an relative coo. value on upper airfoil curve (from 0 to 1) and represents transition point).
You need to know that value from some documentation or Xfoil simulation gives the answer.

All the best,
NV
skinnyfluid is offline   Reply With Quote

Old   July 13, 2010, 09:13
Default
  #4
Senior Member
 
Join Date: Apr 2009
Posts: 531
Rep Power: 20
stumpy is on a distinguished road
The idea of the Gamme Theta (Langtry Menter) transition model is that you don't need to know your transition location - it's predicted as part of the simulation.
stumpy is offline   Reply With Quote

Old   July 13, 2010, 15:55
Default
  #5
New Member
 
NeNaD
Join Date: Mar 2010
Posts: 16
Rep Power: 16
skinnyfluid is on a distinguished road
I have a little practice in CFX but I'll try this model, of course.
That is nice.

Thanx stumpy!
skinnyfluid is offline   Reply With Quote

Old   July 13, 2010, 15:57
Default
  #6
Senior Member
 
Join Date: Apr 2009
Posts: 531
Rep Power: 20
stumpy is on a distinguished road
I think that model should be in Fluent now too?
stumpy is offline   Reply With Quote

Old   July 16, 2010, 06:11
Default
  #7
New Member
 
NeNaD
Join Date: Mar 2010
Posts: 16
Rep Power: 16
skinnyfluid is on a distinguished road
Some corection by myself:

Intermittency Factor is a measure of the probability that a given point is located inside a turbulent region. Upstream of transition the intermittency is zero. Once the transition occurs, the intermittency is ramped up to one until the fully turbulent boundary layer regime is achieved.

All the best,
NV
skinnyfluid is offline   Reply With Quote

Old   July 29, 2010, 12:58
Default
  #8
Senior Member
 
Join Date: Feb 2010
Posts: 148
Rep Power: 17
Jade M is on a distinguished road
In CFX, there is the option for transition with the SST model. The recommended transition model is the Gamma Theta Model developed by Langtry and Menter, which has been developed for standard bypass transition and low free-stream turbulence. The full transition model is based on two transport equations, one for intermittency and one for the transition onset criteria in terms of momentum thickness Reynolds number. There are other choices in CFX as well. The CFX documentation says that this model has been widely validated.
Jade M is offline   Reply With Quote

Old   July 29, 2010, 13:04
Default
  #9
Senior Member
 
Join Date: Feb 2010
Posts: 148
Rep Power: 17
Jade M is on a distinguished road
The FLUENT documentation states:

The transition SST model is based on the coupling of the SST k-omega transport equations with two other transport equations, one for the intermittency and one for the transition onset criteria, in terms of the momentum thickness Reynolds number. An empirical correlation by Langtry and Menter has been developed to cover standard bypass transition as well as flows in low free-stream turbulence environments.

It looks like the same SST transition model is available in CFX and FLUENT, which is not surprising.

It looks like FLUENT also has another transition model available called the k-kl-omega transition model. It is considered to be a three-equation eddy-viscosity type, which includes transport equations for turbulent kinetic energy, laminar kinetic energy and the inverse turbulent time scale.
Jade M is offline   Reply With Quote

Old   February 8, 2016, 02:57
Default
  #10
New Member
 
hossam elbakry
Join Date: Apr 2015
Posts: 7
Rep Power: 10
hossam elbakry is on a distinguished road
but the constants of the transition sst model not the same as the model ( k-omega sst with two tranforms intermittency and transition):

as the constants of the transition sst model:
The transition SST model constants were kept as its default
with following values: Alphan_inf=1, Alpha_inf=0.52,
Alpha_0=0.111, Betan_inf=0.09, a1=0.31 ,Beta_i(Inner)=0.075,
Beta_i (Outer)=0.0828, Ca1=2, Ca2=0.06, Ce1=1, Ce2=50,
C_thetat=0.03, C_s1=2, TKE(Inner)Prandtl=1.176, TKE(Outer)
Prandtl=1, SDR(Inner)Prandtl=2, SDR(Outer)Prandtl=1.168,
Intermit.Prandtl=1, Re_theta.Prandtl=2.
hossam elbakry is offline   Reply With Quote

Reply

Tags
ansys 12, fluent, new turbulence models, sst

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
[Other] How to compute the model by FLUENT and ANSYS njiit ANSYS Meshing & Geometry 1 April 21, 2010 19:05
H ow to compute the model by FLUENT and ANSYS njiit FLUENT 0 March 2, 2010 23:24
FSI, Fluent Ansys coupling Greg Carnie FLUENT 5 January 7, 2010 20:15
Urgent help needed- FLUENT to ANSYS Omer Main CFD Forum 3 September 18, 2006 11:24
Hot News: Ansys Buys Fluent Jonas Larsson Main CFD Forum 23 February 22, 2006 18:12


All times are GMT -4. The time now is 04:24.