CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   STAR-CCM+ (http://www.cfd-online.com/Forums/star-ccm/)
-   -   Model change: k-epsilon to k-omega SST results in divergence (http://www.cfd-online.com/Forums/star-ccm/94721-model-change-k-epsilon-k-omega-sst-results-divergence.html)

kroetenwurz November 23, 2011 11:14

Model change: k-epsilon to k-omega SST results in divergence
 
Hey there,

At first, I am still a beginner in CFD with StarCCM+. :)
I have a simulation of a stirred tank reactor. Using the k-epsilon-model works fine and the solution converges. Now I want to run the same simulation with k-omega SST, but the solution doesn't converge. I didn't change any default values.

Do you have any general advices for me to achieve convergency?

Thank you and best wishes,
kw

kyle November 23, 2011 12:18

Did it diverge or is it just oscillating? If your flow has unsteady features, they will show up more readily with K-omega than K-epsilon, even on a steady state simulation. K-epsilon is more diffusive, so it has a tendency to stamp out these oscillations.

kroetenwurz November 24, 2011 08:31

At first it looked like that it wanted to diverge. I reduced the under-relaxation factors of Segrgated Flow, which helped. Now especially the Sdr-Plot is oscillating between 1e-4 and 1e-5 (no normilization).


All times are GMT -4. The time now is 20:04.