How to incorporate the friction factor....
 

I want to simulate single gas-phase by considering the friction factor. Now the questions are:

(1) when selecting the 'Laminar' viscous model, I amnot sure whether it including the fraction fractor or not? According to the UG manual, it is not clear to me.

(2) If I want to incorporate the UDF friction factor, how can I do? My geometry is simple cylinder pipe.

Please help me out.