Regimes in ultrasound enhanced jet atomization

Under classical conditions, the atomization of a liquid jet moving into a gas occurs primarily via aerodynamic interactions rather than via surface tension as is true for Rayleigh jet break-up. However, ultrasound transferred into the liquid at its source may produce a different mechanism of instability that in turn changes the atomization characteristics. Pressure fluctuation at the interface is still the root cause of instability, but these fluctuations can be driven via acoustic wave patterns transfered through the liquid rather than aerodynamic interactions. We show experimental evidence, including droplet size distribution data and high speed video, that ultrasound in fact measurably changes jet break up in multiple regimes. We perform linear stability analysis on a liquid jet that has a ultrasound induced pressure field imposed on top of a standard velocity field. We then use these results in an energy balance in order to predict the parameter space required for ultrasound to dominate aerodynamic interactions in atomization.