kEqn in kEpsilon.C

 User Name Remember Me Password
 Register Blogs Members List Search Today's Posts Mark Forums Read

 LinkBack Thread Tools Display Modes
 July 20, 2011, 12:35 kEqn in kEpsilon.C #1 Member   fisch Join Date: Feb 2010 Posts: 97 Rep Power: 8 Hello, i try to understand the equations for the k-epsilon turb model. the equation for k is: tmp kEqn ( fvm::ddt(k_) + fvm::div(phi_, k_) - fvm::Sp(fvc::div(phi_), k_) - fvm::laplacian(DkEff(), k_) == G - fvm::Sp(epsilon_/k_, k_) ); i understand all terms except the second and the third... As far as i get it these terms should represent div(k*phi) But how can + fvm::div(phi_, k_) - fvm::Sp(fvc::div(phi_), k_) == div(k*phi) ??? Thanks for any advice, rupert

 July 21, 2011, 05:09 #2 Senior Member   Bernhard Join Date: Sep 2009 Location: Delft Posts: 790 Rep Power: 14 Be aware, that the term in the original equation is equal to which is equal to These are the two terms you see in the kEqn. For a converged solution, the second term vanishes (continuity), but it is numerically favorable to keep it while solving the equation. By the way: origin of fvm::Sp(fvc::div(phi_), epsilon_) in kepsilon Eqn?

 July 22, 2011, 01:21 #3 Member   fisch Join Date: Feb 2010 Posts: 97 Rep Power: 8 Thanks Bernhard, the mentioned origin term (U * grad(k)) was wrong in some of my books ( it was just div(k * U). I had right now a look into the "Turbulent Flows" book of Pope and you're right with the origin of the term... So the question is answered. Thanks again. rupert

 July 22, 2011, 02:53 #4 Senior Member   Bernhard Join Date: Sep 2009 Location: Delft Posts: 790 Rep Power: 14 No, it was nog wrong in the other books, the second term is just zero, since the div(U) = 0

 July 22, 2011, 04:30 #5 Member   fisch Join Date: Feb 2010 Posts: 97 Rep Power: 8 thats right. thanks

 July 22, 2011, 09:24 #6 Member   fisch Join Date: Feb 2010 Posts: 97 Rep Power: 8 I had a look on this k-epsilon calculation and wanted to figure out what happens if wall functions are active. Maybe you know answers to the three following questions, too!? If i use kqR and epsilon wall functions in my calculations he "updates" this G and forces the values for epsilon on the wall region. He's not touching k, right? And as far as i get it this "modified" G is used in the k equation at the wall region, too, right? Is there any documentation about OpenFOAM which formulas were used from the theory (like original equations for kEqn, the wall functions, and so on)??? thanks a lot rupert

 Thread Tools Display Modes Linear Mode

 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 OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post cfd_explorer OpenFOAM Programming & Development 0 March 10, 2011 11:16 cfd_explorer OpenFOAM 0 March 10, 2011 10:58 Zheng.Zhi OpenFOAM 0 August 24, 2009 02:05 tangd OpenFOAM Running, Solving & CFD 2 December 7, 2007 08:54

All times are GMT -4. The time now is 05:22.

 Contact Us - CFD Online - Top