DPM Injection Parameters

Hendawi

Dears fluent users, I'm using the DPM to modelise sprinkler water jet evaporation&drift. In my case, of a continous jet injection from the nozzle exit (just near the nozzle, there's no droplets: the jet is continous), I'm using until now a "plain-orifice-atomizer" injection type. I don't if is it the appropriate model or not!? If yes, does any one have any advise about the 2 questions below: in setting injection parameters step, I didn't well understood what to mean exactly by: 1-the "Number of particle streams"? and what does this parameter have of effect on the initial velocity and droplets siz distribution?

2-the "first point" & "last point" of group injection: the notion of first&last is it relative to space or to time? Hopping that I wasnt very boring,... Best regards