Breakup control of a liquid jet by disturbance manipulation

In this paper, we study the breakup of a circular jet subject to a manipulated disturbance applied by an actuator (here a piezoelectric) in order to control droplets sizes and patterns over a wide range. According to previous studies, breakup of a jet is strongly affected by the characteristics of the disturbance. When the breakup is not periodic and repeatable, it is described as an irregular or random breakup. On the other hand, over a frequency range for the disturbance, the breakup can be made repeatable, though not necessarily uniform, in which the droplets pinch off the stream at a constant rate. In this case, the breakup is called regular, although satellites or secondary droplets might form among the main droplets. In most applications, a very narrow frequency range (much narrower than the regular breakup frequency range) is used for operation, since it is the only range where uniform droplets form. This work demonstrates that by eliminating secondary droplets or satellites, the entire regular breakup regime becomes available for desirable operation, i.e., uniform droplet generation. The regular breakup regime is specified experimentally and an additional disturbance is added to the driving disturbance in order to eliminate the nonuniform droplets. This method provides us with droplets of the desired size when they cannot be produced with a single frequency disturbance alone. The results also demonstrate that different frequencies for the additional disturbance produce different patterns for the droplets sizes.