Atomizers used in practical applications such as fuel injectors and paint applicators do not produce sprays of uniform droplet size.Instead,the spray is a collection of droplets that encompass a range of different sizes.During the spray flight from the nozzle to the target droplets are broken at various regimes: primary and secondary before reaching a coalescence stage.In the first two stages the ligaments are broken due to competing mechanisms of shear or inertia,surface tension,and viscous forces.The ratio of surface tension to shear or inertial forces is defined as the non-dimensional Weber number.Increasing the Weber number will result to change in the mechanism of droplet formation ranging from stable without breakup,to bag breakup,sheet striping as the Weber number increases.In this paper the investigators studied secondary breakup and the percentage of the various breakup mechanisms as a function of the location between the nozzle and the target.The team used laser diffraction to measure droplet size distribution along the center of the spray envelope.It was found that during the first 20 cm from the nozzle various breakup mechanisms take place before all droplets become stable and coalescence starts.The interaction between the liquid and gas is affected by the pressure of the gas and liquid flow.