convergence issue in LES

Deb

Hi guys

i am trying to solve a problem where two fluids ch4 (at 300K, vel ~1m/s) and air (750K, vel ~20m/s) flowing co-axially (ch4 in the inner tube and air in the outer tube. these tubes are separated by a wall till some distance after which both fluids will be allowed to mix in a single tube) allowed to mix in a single tube. I am trying to start LES model from a (k-e, realizable and laminar flamelet converged solution. But in all cases the Tmax and Texit at the outlet are highly oscillatory (these two are my monitor points) and the solution looks unphysical (from the contour plots we can see). Does anybody have a clue on it? plz let me know.

Thanks Deb