As mentioned by Filippo, using or not a model for turbulence is not among the things you can choose. For given setup and conditions you either have to or don't have to actually use it.

However, in practical terms, as the most common turbulence models increase the resulting viscosity of the flow, the answer to what you found is yes, adding a turbulence model typically makes it easier, all the things equal, to get to a converged steady state. But, again, you can't really use it like this.

Your questione makes no real sense.

You have to set a model that is suitable for your physics, if your flow problem is laminar you must get a laminar convergent solution. That is a viscous flow, can be also unsteady (for example the laminar vortex shedding) but you have to be able to solve. Otherwise your numerical model is simply wrong.

Setting a turbulent model in a certain formulation means you want to solve the statistically averaging equation (RANS/URANS) or the filtered equations (LES) in a flow problem that has turbulence.

Thanks Filippo Maria Denaro .

maybe as I am dealing with multi-phase phase thermal phase change problem, laminar consideration is wrong.

Dear Soumitra Vadnerkar

Your experience is not usual. Normally, the laminar model is easier to converge than turbulence model, because there is more equations to be solved. So, please make sure that any options in both modeling is right. My question is: what is the real regime of the flow, laminar or turbulent or transition?

As mentioned by Filippo, using or not a model for turbulence is not among the things you can choose. For given setup and conditions you either have to or don't have to actually use it.

However, in practical terms, as the most common turbulence models increase the resulting viscosity of the flow, the answer to what you found is yes, adding a turbulence model typically makes it easier, all the things equal, to get to a converged steady state. But, again, you can't really use it like this.