Transition to laminar in free shear turbulent flows
 

Hello everyone,

Does anyone know how to model transition from turbulent to laminar in free shear flows using URANS? I could only find transition models for boundary layers in FLUENT, but not for free shear.

I have implemented a UDF which damps the turbulent viscosity when the cell Reynolds number goes below 5000, and sets it to zero when it reaches 3000. I obtained much better results than with the standard formulation of the turbulent viscosity, only some minor oscillations in the velocity were observed. However, the lengthscale of the Reynolds number seems to me as a quite arbitrary parameter, which, depending on what you set, will give an earlier or later transition.
FLUENT cell based Reynolds number used the cell size. This seems to be even more arbitrary since, (i) it is mesh dependent, and (ii) does not depend in the actual geometry of the domain.

Does anyone know about a more elaborate model (which can be used in URANS) to accout for this transition?

Thanks in advance!