Is there an equation for predicting when a stream breaks into droplets?

[leorex]

I was just wondering, is there any equation which predicts when does a stream of liquid( e.g water, ethanol) break into droplets? i think it relates to the speed and diameter of the stream, probably also with diameter, but i cannot find any equations which governs the rule

 

[Andy Resnick]

google "rayleigh instability".