flow simulation in nozzle
 

Hi All,
Hope everyone doing well.
I am trying to simulate a showerhead nozzle.

objective:
I have to see how the flow is happening when water exiting the nozzle of the shower head and analyze how flow is spreading, is there any reverse flow of air into the nozzle

initially it will be having air and when flow starts coming from chamber, it will push the air inside and flow comes out of it. so i need to consider both air and water as fluid and do a multiphase simulation.

my questions are:
what should be primary phase and what should be secondary phase for my problem?
I read some examples and all have taken continuous phase as primary like humid air with air as 1ary and water as 2ary; fluid bed with pumping fluid as primary and bed as secondary.

what model will exactly suits my application VOF or Eularian approach. what should be considered when using these models.

any lead or help in this regard will be greatly appreciated
Thanks in advance

for the same problem i tried simulation using Eulerian multiphase model
but flow from the nozzle exit not happening like jet. instead its spreading along the walls and sticking to it. ideally it should eject like a jet (i believe)
I have attached screenshots of water volume fraction contours.
along with this the velocities are also not proper. when i did with single phase where whole domain is initialized with water, velocities are as expected. but not now
Hope someone will guide me in where simulation setup went wrong