[lili]

hi
I want to model a plain orifice atomizer. in fluent help it says the required parameters are:
nozzle diameter
nozzle length
radius of curvature of the inlet corner
upstream pressure
downstream pressure
viscosity
liquid density
vapor pressure
while in set injection properties panel the required parameters are: the position of injection point (x,y,z), axis (x,y,z), temperature, flow rate, vapor pressure, injector inner diameter and orifice length, corner radius of curvature, constant A, azimuthal start and stop angle.
why these parameters are different from those exist in help? and what is constant A? is it: Ca=3+L/3.6d (L orifice length and d orifice diameter)