Thanks Messrs. Hydrae and DMcGrath,your answers confirmed what I thought I should do. But now what should be the emitter coefficient do you suggest I should use to model an open pipe?
Model the pipe as it is, diameter, length, roughness
add in any minor losses such as entrance, reentrance, 90, tees, valves, ect, the end of the pipe is the efficient nozzle as DMcGrath pointed out.
Hydrae