How to enforce laminar flow while using k-e

Grzegorz Kondora

Hello everybody,

I'm modelling some kind of mixing tank, in which flow has a dual character - laminar and turbulent. Based on the strain rate criterion I can decide which character of flow I would like to have. As far as I know FLUENT has an option, available in fluid zone, called Laminar Zone which can be used to enforce laminar flow while using turbulence visocus model. But this works only if the laminar zone is known, so separate fluid zone can be created during mesh generation. I know that in order to disable turbulence there is a need to turn off kinetic energy production and set turbulence viscosity to zero. I have made several attempts. Results are as follows: DEFINE_TURBULENT_VISCOSITY works well (in regions where I would like to have 0 is 0, elsewhere is set to C_MU_T(c,t)). The problem is I don't know how to set kinetic energy (or production of kinetic energy) to 0. I have tried: 1) DEFINE_ADJUST - leads to divergence; 2) source term set to 0, does not affect production of k at all, since source is one of terms in k equation; 3) fixed value option - works well if you know value of C_K in whole domain, so it sets 0 where you want, but do not sets value of real C_K elsewhere, because k equation is not calculated (k residual always equal to 0). Does anybody knows how to disable turbulence in some regions (set C_K to zero or disable production of k)? Thank you very much for your help in advance.

Grzegorz Kondora