SIMPLE algorithm and k-eps turbulence model
 

I'm using SIMPLE-based control volume method and K-eps model to calculate the flow fields around airfoils,but when I use much more grids or highly stretched grids near the solid surface, the computation diverges,I don't know what caused this. Can anyone help me with that? thanks!

Zhang

a suggestion
 

keep an eye on the n+ value. See whether the code diverges when n+ is < 11.63 in one of the cells? If that is the case, then derive the value of G, epsilon & wall shear stress using linear velocity profile !

Re: a suggestion
 

If y+ is getting small this can get tricky indeed, as you may not be respecting your model's assumptions. In Aero applications Low-Re k-E models are much more adapted as well as Shear Stress Transport k-Omega type models where you integrate to the walls.

Re: a suggestion
 

Dear Abhi

What's the meaning of G in your suggestion?

YANG

Re: a suggestion
 

Hi, Abhi

What's the lower limit of n+ for k-epsilon model near the solid wall?

Thanks YANG

Re: a suggestion
 

Yang,

You should read CFD textbook materials! Details about most classical models, their applications and restrictions can be found in the books by Versteeg and Malalasekera (1995) or Wilcox (1993) for a more exhaustive approach. These are only suggestions of reading; there exist a lot more. In these anyway you would find explanations on P and G terms (G is the production term due to body force in general) and a lot more...

Re: a suggestion
 

Dear Holidays

Thanks a lot for you patient help.

YANG

Re: a suggestion
 

"G is the production term due to body force in general" - it originates when you go for Reynold's averaging. Look at the viscous dissipation.

Re: a suggestion
 

G is of the form Gbuoy (+Grot + Gresist) with Gbuoy which can be written as -Mu_effective/(Rho*Sigma_Rho)*g*GradRho, ie a term that accounts for buoyancy and body force effects...

Re: a suggestion
 

Was the question first coined by YANG ? Yang , give me some more inputs abt the way ur code is behaving. May be I can suggest something. READ Turbulent Flows by STEFAN POPE if u have not!!!!!!! A very very good book

Re: SIMPLE algorithm and k-eps turbulence model
 

i am using the TEACH-T code which uses the SIMPLE algorithm and K-E model and i want to modify it to solve unsteady problem what type of code ur using and what do u think of TEACH-T and could the modification be easily accomplished

Hi,
Would you please send me the TEACH-T code.
Thanks a lot.
my email : ghorbani.mec@gmail.com