CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Running, Solving & CFD

Problem with LaunderSharma compressible turbulence model wrong formulation

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   July 3, 2006, 04:39
Default maybe I'm not right, but in La
  #1
Member
 
Luca M.
Join Date: Mar 2009
Location: Luzern, Switzerland
Posts: 59
Rep Power: 17
luca is on a distinguished road
maybe I'm not right, but in LaunderSharma compressible model Epsilon equation, we have that :

... + fvm::SuSp((C3 - 2.0/3.0*C1)*rho_*divU, epsilon_)

and in the default turbulenceProperties file we have:

C3 = -0.33

I think that we have to change the default value of C3 as:

C3 = 0.33

or we have to change the formulation of Epsilon eq. as:

... + fvm::SuSp((- C3 - 2.0/3.0*C1)*rho_*divU, epsilon_) or

... - fvm::SuSp(( C3 + 2.0/3.0*C1)*rho_*divU, epsilon_)

because the term C3*rho_*divU has to be positive in RHS of Epsilon equation.

I'm right ?!?

Luca
luca is offline   Reply With Quote

Old   July 3, 2006, 06:34
Default Please post a bug report (in O
  #2
Senior Member
 
Mattijs Janssens
Join Date: Mar 2009
Posts: 1,419
Rep Power: 26
mattijs is on a distinguished road
Please post a bug report (in OpenFOAM-bugs) if you think it is incorrect.
mattijs is offline   Reply With Quote

Old   July 3, 2006, 06:37
Default Nope - this is to do with the
  #3
Senior Member
 
Hrvoje Jasak
Join Date: Mar 2009
Location: London, England
Posts: 1,907
Rep Power: 33
hjasak will become famous soon enough
Nope - this is to do with the C3 term in engines simulations, where it turns out that a "small positive constant" C3 actually needs to be negative to get the right behaviour. Find an old-ish engines modelling Thesis from Imperial College and you will find the details.

Hrv
__________________
Hrvoje Jasak
Providing commercial FOAM/OpenFOAM and CFD Consulting: http://wikki.co.uk
hjasak is offline   Reply With Quote

Old   July 3, 2006, 07:21
Default so why we have different formu
  #4
Member
 
Luca M.
Join Date: Mar 2009
Location: Luzern, Switzerland
Posts: 59
Rep Power: 17
luca is on a distinguished road
so why we have different formulation in epsilon Eqn. between LaunderSharmaKE and kEpsilon turbulence model, (except f2() term)

kEpsilon

C1*G*epsilon_/k_
- fvm::SuSp(((2.0/3.0)*C1 + C3)*rho_*divU, epsilon_)
- fvm::Sp(C2*rho_*epsilon_/k_, epsilon_)


LaunderSharmaKE

C1*G*epsilon_/k_
+ fvm::SuSp((C3 - 2.0/3.0*C1)*rho_*divU, epsilon_)
- fvm::Sp(C2*f2()*rho_*epsilon_/k_, epsilon_)


Luca
luca is offline   Reply With Quote

Old   July 3, 2006, 07:24
Default In that case: hmm. What does
  #5
Senior Member
 
Hrvoje Jasak
Join Date: Mar 2009
Location: London, England
Posts: 1,907
Rep Power: 33
hjasak will become famous soon enough
In that case: hmm. What does the original paper say?

Hrv
__________________
Hrvoje Jasak
Providing commercial FOAM/OpenFOAM and CFD Consulting: http://wikki.co.uk
hjasak 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
Compressible Turbulence Model Implementations shaun OpenFOAM Running, Solving & CFD 4 October 21, 2009 12:55
compressible turbulence model shuo Main CFD Forum 3 December 22, 2007 10:51
Problem calculate Y in compressible turbulence model luca OpenFOAM Running, Solving & CFD 5 June 1, 2006 06:53
viscous force: Cfx : wrong formulation ???? tommy CFX 0 May 11, 2006 10:17
Steady state formulation of turbulence ?? Jitendra Main CFD Forum 1 June 27, 2000 19:49


All times are GMT -4. The time now is 17:13.