|
[Sponsors] |
January 6, 2003, 12:59 |
k-w turbulence model
|
#1 |
Guest
Posts: n/a
|
Recently I have been investigating the Wilcox k-w turbulence model, and I have a question that hopefully someone(s) can help me with.
Wilcox cites the A.A. Townsend approximation for k as k~t^(-n). I am unclear about what time span the "t" is referring to. Looks like the units don't match, though I'm not sure if they have to in this case. An explanation of the equation and the "t" would be greatly appreciated. Thanks in advance. |
|
January 7, 2003, 14:21 |
k-w turbulence model: update
|
#2 |
Guest
Posts: n/a
|
After reviewing the equation, my colleagues and I can only conclude that the "t" is actually a "Tau" or a stress tensor without subscripts, and not a time scale or time span. So at a minimum, its a confusing simplification, and possibly a typo. Any comments?
|
|
January 8, 2003, 05:33 |
Re: k-w turbulence model: update
|
#3 |
Guest
Posts: n/a
|
I'm assuming you're referring to Wilcox's turbulence and CFD book published by DCW industries.
They have a web page devoted to known typos, and reporting newly-discovered ones: http://www.dcwindustries.com/typos.htm I suggest you check it out! Good luck |
|
January 8, 2003, 20:59 |
Re: k-w turbulence model: final word
|
#4 |
Guest
Posts: n/a
|
After sharing e-mails with the author, I've learned that the equation is correct as written k~t^(-n) and t is indeed time. The time scale for this t is infinity and leads to the asymptotic solution for k.
|
|
January 20, 2003, 09:58 |
Re: k-w turbulence model: final word
|
#5 |
Guest
Posts: n/a
|
Townsend gives the relation k~t^-n for the (initial) decaying (grid) turbulence and give n the value = 1.25+-0.06. Note that n rises to 2.5 in the final decay. This physical behaviour is one (good) reason for introducing turbulence govern (NOT y+) damping functions. Wilcox and others uses this relation to set the value of the coefficient for the destruction term (C_eps2, beta) in the epsilon/omega-equation.
/Jonas |
|
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Wrong calculation of nut in the kOmegaSST turbulence model | FelixL | OpenFOAM Bugs | 27 | March 27, 2012 09:02 |
Low Reynolds k-epsilon model | YJZ | ANSYS | 1 | August 20, 2010 13:57 |
KOmega Turbulence model from wwwopenFOAMWikinet | philippose | OpenFOAM Running, Solving & CFD | 30 | August 4, 2010 10:26 |
Fan heater model: what turbulence source to use? | andy20 | CFX | 7 | March 3, 2008 16:42 |
SSG Reynolds Turbulence Model | Georges | CFX | 1 | February 28, 2007 16:15 |