Acoustic emulsification. Part 2. Breakup of the large primary oil droplets in a water medium

Abstract

A theoretical model is presented for the liquid-liquid emulsification phenomenon based on the deformation and breakup of an oil droplet exposed to a cavitation shock wave generated by an acoustic field. The model predicts a relationship between the Ohnesorge number and the critical Weber number ratio for long acoustic irradiation times. At short irradiation times, the mean particle size and variance decrease with increasing time of acoustic irradiation. The results show remarkable agreement when compared with results obtained from the studies on liquid droplets exposed to shock impact from a gas stream. The mechanism for acoustic emulsification is that large oil droplets originally formed from the instability oil-water interface are disintegrated into smaller ones by the cavitation until a critical size, characteristic of the particular oil-water system, is reached.