Fluid flow through a domain

I am simulating the flow from these (3 inlets) 8 attached figure untill the top of the plate where my outlet is located. 


I am using the following BC 


Inlet - Pressure Inlet 
Outlet - Mass flow outlet 

I am working on inlet pressures between 6- 24 bars . Do i need to use K epsilon or k omega turbulence models currently i am running my simulations in laminar model 

Due to high pressure of 6-24 bar as enough turbulence is generated do i need to select a turbulence model 

Also to get accurate results how fine should my mesh or the skewness of the mesh elements be ?