Choosing Time step size ??
 

Hello guys i am kinda new to FLUENT . I am working to simulate some cases on the micro-channel be it y shaped or t shaped or a basic one.
I have like two questions to ask
Firstly, I want to know how do you decide on the time step size when you begin the iterations .
Secondly, Me being new ain't that good with the background concepts of many options that show up in the GUI say for example : when goto DEFINE->phases choose some phase and hit set for solid u get a bunch of properties like granular bulk viscosity , frictional viscosity , frictional pressure, granular temperature etc. and each having its own lists of options . So i think it would be very nice of u guys to help me out with those , you could just gimme a lead regarding it ,say a website URL or a book ,from which i can get a clear understanding about the options in FLUENT .

Thanks
Tarun