Break-up dynamics and drop size distributions created from spiralling liquid jets

The dynamics of the break-up of spiralling jets of Newtonian liquids were visualised. The jets were created from orifices at the bottom of a 0.085-m-diameter can rotating about its vertical axis and imaged using a high-speed camera. The effects of liquid dynamic viscosity (0.001–0.09 Pa s), rotation rate (5–31 rad s−1) and orifice size (0.001 and 0.003 m) upon the jet break-up and drop size distributions produced in the Rayleigh regime were investigated. The ranges of dimensionless parameters were 1<Re<103, 0.2<Rb<4, 0.5<We<25 and 5×10−3<Oh<4×10−1. Four generic break-up modes identified were a strong function of dynamic viscosity and jet exit velocity. A flow pattern map of Ohnesorge number against Weber number enabled prediction of these modes. Increasing the can rotation rate increases jet exit velocity due to centrifugal forces and the trajectory of the jet becomes more curved. The break-up dynamics of the jets were non-linear, although some agreement between measured break-up lengths with the linear stability analysis developed previously was noted at low Reynolds numbers. A non-linear theoretical analysis is required to elucidate the important features.