Liquid rotary jet fragmentation of a pressure atomizer

Rotary water jets are commonly used in the world of agriculture, particularly in irrigation and in treatment with pesticides in the form of micro-sprinklers. However, their study is not very well developed, even though the problems linked to water resource losses or the drift of pesticides in the atmosphere are well known. Controlling the size distribution of the drops that are generated becomes essential to avoid these problems. The observation of the fragmentation of a rotating jet is implemented in this study. The shadowgraphy method coupled with a drop size and velocity detection algorithm has been adapted for this rotating system. Different modes of rupture can be observed and drop size distributions are analyzed. Primary atomization is controlled by the orthoradial air velocity generated by the rotation and by the stretching of the ligaments due to the Coriolis and centrifugal forces. We compare the different modes of fragmentation as a function of the aerodynamic forces created by the rotation and the momentum flux of the water jet in the air.