I work with mist heads and a bit more complicated atomizers and found that the same heads mounted on risers and 'hanged' from a ceiling generate different wetted radii. Hanging ones were giving a longer throw, but could not relate that to any function of a stem length (for water mist therr is also a problem of humidity and secondary breakup, you do not have). Another issue is that the avergage droplet size also influences the distance droplets travel, as it is related to the shape drag generated by every single travelling droplet moving in still air. In short, I believe there is no general or suitable formula, but you may have a chance in relating experimentally found wetted radii for sprinkler heads instaled on risers and for the 'hanging' ones.

Thank you Jerzy for your answer,

The droplet size is directly related to the pressure head and the nozzle diameter, that's why I didn't mention it in the factors affecting the throw.

Dear Mohammad,

You might read the book of Jack-Keller (Sprinkle and Trikle irrigation...) and found relations there...

Many thanks Fulvio, Keller's book is really important and I appreciate the e-Copy you kindly sent.

Water application profiles for a single Nelson R33 sprinkler at various pressures

Water application profiles for a single Rainbird Mini Paw/LG-3 sprinkler at various pressures

Dear Mohammad,

You can use the empirical model developed by Heermann and Stahl (2006) to predict the wetted radius as a function of the nozzle diameter and the nozzle pressure. For more information you can go to the following reference: Martin, D.L., Kincaid, D.C., Lyle, W.M. (2007). Design and operation of sprinkler systems. In: Design and operation of farm irrigation systems, Glenn J. Hoffman, Ed., American Society of Agricultural and Biological Engineers, St. Joseph. pp. 557-631.