Turbulent primary breakup of round and plane liquid jets in still air

Abstract

The formation of drops at the surface of turbulent liquids, e.g., turbulent primary breakup, was studied experimentally. Pulsed shadowgraphy and holography were used to observe the properties of the liquid surface and the drops formed by turbulent primary breakup. Measured properties included liquid surface velocities, conditions at the onset of ligament and drop formation, ligament and drop sizes, ligament and drop velocities and rates of drop formation. Phenomenological theories were used to help interpret and correlate the measurements. Present results show that the onset of ligament formation occurs once the kinetic energy of the turbulent eddies that form the ligaments exceeds the required surface tension energy of a ligament of comparable size. Subsequently, the onset of drop formation occurs once drops form at the tips of ligaments due to Rayleigh breakup. This same mechanism controls the subsequent variation of drop sizes due to turbulent primary breakup as a function of distance from the jet exit. In addition, ligament and drop velocities were associated with mean and fluctuating velocities of the liquid, and rates of drop formation could be expressed by surface efficiency factors defined as the fraction of the maximum cross stream liquid mass flux.