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-   -   Values of k and omega at the wall (http://www.cfd-online.com/Forums/fluent/47370-values-k-omega-wall.html)

oldah February 19, 2008 11:52

Values of k and omega at the wall
 
Hi,

I'm running a k-omega model on a pure natural convection flow around a horizontal cylinder. The flow is in the turbulent regime and as such a transition over the cylinder is expected. I've found that the roughness height controls where the transition point is and without any roughness there is no transition.

I have looked at the wall boundary value for omega in the manual, which includes the roughness height, but I can't find how the value of k is calculated and if the roughness height is included in these equations? Could someone refer me to these equations?

The reason that I'm so interested in how the roughness is used in the solution equations is that the k-omega model is the only model in Fluent 6.3 and Fluent 12 which will produce a solution which exhibits transitions phenomena.

best regards - Ola

Ralf Schmidt February 20, 2008 03:50

Re: Values of k and omega at the wall
 
hi!

as i know, k is zero at the wall. It is difined from the turbulent fluctuations of the velocity - and these are allways zero az the wall!

Hope, it helps Ralf

oldah February 22, 2008 04:08

Re: Values of k and omega at the wall
 
Indeed the velocities at the wall are zero but the TKE is non-zero at the wall, how can this be? There must be something I'm doing wrong when plotting and displaying contours over the TKE, no?

I'm using k-omega on a horizontal cylinder, y+ = 1.6.



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